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• Generate lags R

  - by Btibert3

  Hi All, I hope this is basic; just need a nudge in the right direction. I have read in a database table from MS Access into a data frame using RODBC. Here is a basic structure of what I read in: PRODID PROD Year Week QTY SALES INVOICE Here is the structure: str(data) 'data.frame': 8270 obs. of 7 variables: $ PRODID : int 20001 20001 20001 100001 100001 100001 100001 100001 100001 100001 ... $ PROD : Factor w/ 1239 levels "1% 20qt Box",..: 335 335 335 128 128 128 128 128 128 128 ... $ Year : int 2010 2010 2010 2009 2009 2009 2009 2009 2009 2010 ... $ Week : int 12 18 19 14 15 16 17 18 19 9 ... $ QTY : num 1 1 0 135 300 270 300 270 315 315 ... $ SALES : num 15.5 0 -13.9 243 540 ... $ INVOICES: num 1 1 2 5 11 11 10 11 11 12 ... Here are the top few rows: head(data, n=10) PRODID PROD Year Week QTY SALES INVOICES 1 20001 Dolie 12" 2010 12 1 15.46 1 2 20001 Dolie 12" 2010 18 1 0.00 1 3 20001 Dolie 12" 2010 19 0 -13.88 2 4 100001 Cage Free Eggs 2009 14 135 243.00 5 5 100001 Cage Free Eggs 2009 15 300 540.00 11 6 100001 Cage Free Eggs 2009 16 270 486.00 11 7 100001 Cage Free Eggs 2009 17 300 540.00 10 8 100001 Cage Free Eggs 2009 18 270 486.00 11 9 100001 Cage Free Eggs 2009 19 315 567.00 11 10 100001 Cage Free Eggs 2010 9 315 569.25 12 I simply want to generate lags for QTY, SALES, INVOICE for each product but I am not sure where to start. I know R is great with Time Series, but I am not sure where to start. I have two questions: 1- I have the raw invoice data but have aggregated it for reporting purposes. Would it be easier if I didn't aggregate the data? 2- Regardless of aggregation or not, what functions will I need to loop over each product and generate the lags as I need them? In short, I want to loop over a set of records, calculate lags for a product (if possible), append the lags (as they apply) to the current record for each product, and write the results back to a table in my database for my reporting software to use. Any help you can provide will be greatly appreciated! Many thanks in advance, Brock

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• How to move a kinect skeleton to another position

  - by Ewerton

  I am working on a extension method to move one skeleton to a desired position in the kinect field os view. My code receives a skeleton to be moved and the destiny position, i calculate the distance between the received skeleton hip center and the destiny position to find how much to move, then a iterate in the joint applying this factor. My code, actualy looks like this. public static Skeleton MoveTo(this Skeleton skToBeMoved, Vector4 destiny) { Joint newJoint = new Joint(); ///Based on the HipCenter (i dont know if it is reliable, seems it is.) float howMuchMoveToX = Math.Abs(skToBeMoved.Joints[JointType.HipCenter].Position.X - destiny.X); float howMuchMoveToY = Math.Abs(skToBeMoved.Joints[JointType.HipCenter].Position.Y - destiny.Y); float howMuchMoveToZ = Math.Abs(skToBeMoved.Joints[JointType.HipCenter].Position.Z - destiny.Z); float howMuchToMultiply = 1; // Iterate in the 20 Joints foreach (JointType item in Enum.GetValues(typeof(JointType))) { newJoint = skToBeMoved.Joints[item]; // This adjust, try to keeps the skToBeMoved in the desired position if (newJoint.Position.X < 0) howMuchToMultiply = 1; // if the point is in a negative position, carry it to a "more positive" position else howMuchToMultiply = -1; // if the point is in a positive position, carry it to a "more negative" position // applying the new values to the joint SkeletonPoint pos = new SkeletonPoint() { X = newJoint.Position.X + (howMuchMoveToX * howMuchToMultiply), Y = newJoint.Position.Y, // * (float)whatToMultiplyY, Z = newJoint.Position.Z, // * (float)whatToMultiplyZ }; newJoint.Position = pos; skToBeMoved.Joints[item] = newJoint; //if (skToBeMoved.Joints[JointType.HipCenter].Position.X < 0) //{ // if (item == JointType.HandLeft) // { // if (skToBeMoved.Joints[item].Position.X > 0) // { // } // } //} } return skToBeMoved; } Actualy, only X position is considered. Now, THE PROBLEM: If i stand in a negative position, and move my hand to a positive position, a have a strange behavior, look this image To reproduce this behaviour you could use this code using (SkeletonFrame frame = e.OpenSkeletonFrame()) { if (frame == null) return new Skeleton(); if (skeletons == null || skeletons.Length != frame.SkeletonArrayLength) { skeletons = new Skeleton[frame.SkeletonArrayLength]; } frame.CopySkeletonDataTo(skeletons); Skeleton skeletonToTest = skeletons.Where(s => s.TrackingState == SkeletonTrackingState.Tracked).FirstOrDefault(); Vector4 newPosition = new Vector4(); newPosition.X = -0.03412333f; newPosition.Y = 0.0407479f; newPosition.Z = 1.927342f; newPosition.W = 0; // ignored skeletonToTest.MoveTo(newPosition); } I know, this is simple math, but i cant figure it out why this is happen. Any help will be apreciated.

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• Stepping into Ruby Meta-Programming: Generating proxy methods for multiple internal methods

  - by mstksg

  Hi all; I've multiply heard Ruby touted for its super spectacular meta-programming capabilities, and I was wondering if anyone could help me get started with this problem. I have a class that works as an "archive" of sorts, with internal methods that process and output data based on an input. However, the items in the archive in the class itself are represented and processed with integers, for performance purposes. The actual items outside of the archive are known by their string representation, which is simply number_representation.to_s(36). Because of this, I have hooked up each internal method with a "proxy method" that converts the input into the integer form that the archive recognizes, runs the internal method, and converts the output (either a single other item, or a collection of them) back into strings. The naming convention is this: internal methods are represented by _method_name; their corresponding proxy method is represented by method_name, with no leading underscore. For example: class Archive ## PROXY METHODS ## ## input: string representation of id's ## output: string representation of id's def do_something_with id result = _do_something_with id.to_i(36) return nil if result == nil return result.to_s(36) end def do_something_with_pair id_1,id_2 result = _do_something_with_pair id_1.to_i(36), id_2.to_i(36) return nil if result == nil return result.to_s(36) end def do_something_with_these ids result = _do_something_with_these ids.map { |n| n.to_i(36) } return nil if result == nil return result.to_s(36) end def get_many_from id result = _get_many_from id return nil if result == nil # no sparse arrays returned return result.map { |n| n.to_s(36) } end ## INTERNAL METHODS ## ## input: integer representation of id's ## output: integer representation of id's def _do_something_with id # does something with one integer-represented id, # returning an id represented as an integer end def do_something_with_pair id_1,id_2 # does something with two integer-represented id's, # returning an id represented as an integer end def _do_something_with_these ids # does something with multiple integer ids, # returning an id represented as an integer end def _get_many_from id # does something with one integer-represented id, # returns a collection of id's represented as integers end end There are a couple of reasons why I can't just convert them if id.class == String at the beginning of the internal methods: These internal methods are somewhat computationally-intensive recursive functions, and I don't want the overhead of checking multiple times at every step There is no way, without adding an extra parameter, to tell whether or not to re-convert at the end I want to think of this as an exercise in understanding ruby meta-programming Does anyone have any ideas? edit The solution I'd like would preferably be able to take an array of method names @@PROXY_METHODS = [:do_something_with, :do_something_with_pair, :do_something_with_these, :get_many_from] iterate through them, and in each iteration, put out the proxy method. I'm not sure what would be done with the arguments, but is there a way to test for arguments of a method? If not, then simple duck typing/analogous concept would do as well.

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• Hibernate3: Self-Referencing Objects

  - by monojohnny

  Need some help on understanding how to do this; I'm going to be running recursive 'find' on a file system and I want to keep the information in a single DB table - with a self-referencing hierarchial structure: This is my DB Table structure I want to populate. DirObject Table: id int NOT NULL, name varchar(255) NOT NULL, parentid int NOT NULL); Here is the proposed Java Class I want to map (Fields only shown): public DirObject { int id; String name; DirObject parent; ... For the 'root' directory was going to use parentid=0; real ids will start at 1, and ideally I want hibernate to autogenerate the ids. Can somebody provide a suggested mapping file for this please; as a secondary question I thought about doing the Java Class like this instead: public DirObject { int id; String name; List<DirObject> subdirs; Could I use the same data model for either of these two methods ? (With a different mapping file of course). --- UPDATE: so I tried the mapping file suggested below (thanks!), repeated here for reference: <hibernate-mapping> <class name="my.proj.DirObject" table="category"> ... <set name="subDirs" lazy="true" inverse="true"> <key column="parentId"/> <one-to-many class="my.proj.DirObject"/> </set> <many-to-one name="parent" class="my.proj.DirObject" column="parentId" cascade="all" /> </class> ...and altered my Java class to have BOTH 'parentid' and 'getSubDirs' [returning a 'HashSet']. This appears to work - thanks, but this is the test code I used to drive this - I think I'm not doing something right here, because I thought Hibernate would take care of saving the subordinate objects in the Set without me having to do this explicitly ? DirObject dirobject=new DirObject(); dirobject.setName("/files"); dirobject.setParent(dirobject); DirObject d1, d2; d1=new DirObject(); d1.setName("subdir1"); d1.setParent(dirobject); d2=new DirObject(); d2.setName("subdir2"); d2.setParent(dirobject); HashSet<DirObject> subdirs=new HashSet<DirObject>(); subdirs.add(d1); subdirs.add(d2); dirobject.setSubdirs(subdirs); session.save(dirobject); session.save(d1); session.save(d2);

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• GHC.Generics and Type Families

  - by jberryman

  This is a question related to my module here, and is simplified a bit. It's also related to this previous question, in which I oversimplified my problem and didn't get the answer I was looking for. I hope this isn't too specific, and please change the title if you can think if a better one. Background My module uses a concurrent chan, split into a read side and write side. I use a special class with an associated type synonym to support polymorphic channel "joins": {-# LANGUAGE TypeFamilies #-} class Sources s where type Joined s newJoinedChan :: IO (s, Messages (Joined s)) -- NOT EXPORTED --output and input sides of channel: data Messages a -- NOT EXPORTED data Mailbox a instance Sources (Mailbox a) where type Joined (Mailbox a) = a newJoinedChan = undefined instance (Sources a, Sources b)=> Sources (a,b) where type Joined (a,b) = (Joined a, Joined b) newJoinedChan = undefined -- and so on for tuples of 3,4,5... The code above allows us to do this kind of thing: example = do (mb , msgsA) <- newJoinedChan ((mb1, mb2), msgsB) <- newJoinedChan --say that: msgsA, msgsB :: Messages (Int,Int) --and: mb :: Mailbox (Int,Int) -- mb1,mb2 :: Mailbox Int We have a recursive action called a Behavior that we can run on the messages we pull out of the "read" end of the channel: newtype Behavior a = Behavior (a -> IO (Behavior a)) runBehaviorOn :: Behavior a -> Messages a -> IO () -- NOT EXPORTED This would allow us to run a Behavior (Int,Int) on either of msgsA or msgsB, where in the second case both Ints in the tuple it receives actually came through separate Mailboxes. This is all tied together for the user in the exposed spawn function spawn :: (Sources s) => Behavior (Joined s) -> IO s ...which calls newJoinedChan and runBehaviorOn, and returns the input Sources. What I'd like to do I'd like users to be able to create a Behavior of arbitrary product type (not just tuples) , so for instance we could run a Behavior (Pair Int Int) on the example Messages above. I'd like to do this with GHC.Generics while still having a polymorphic Sources, but can't manage to make it work. spawn :: (Sources s, Generic (Joined s), Rep (Joined s) ~ ??) => Behavior (Joined s) -> IO s The parts of the above example that are actually exposed in the API are the fst of the newJoinedChan action, and Behaviors, so an acceptable solution can modify one or all of runBehaviorOn or the snd of newJoinedChan. I'll also be extending the API above to support sums (not implemented yet) like Behavior (Either a b) so I hoped GHC.Generics would work for me. Questions Is there a way I can extend the API above to support arbitrary Generic a=> Behavior a? If not using GHC's Generics, are there other ways I can get the API I want with minimal end-user pain (i.e. they just have to add a deriving clause to their type)?

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• All possible combinations of length 8 in a 2d array

  - by CodeJunki

  Hi, I've been trying to solve a problem in combinations. I have a matrix 6X6 i'm trying to find all combinations of length 8 in the matrix. I have to move from neighbor to neighbor form each row,column position and i wrote a recursive program which generates the combination but the problem is it generates a lot of duplicates as well and hence is inefficient. I would like to know how could i eliminate calculating duplicates and save time. int a={{1,2,3,4,5,6}, {8,9,1,2,3,4}, {5,6,7,8,9,1}, {2,3,4,5,6,7}, {8,9,1,2,3,4}, {5,6,7,8,9,1}, } void genSeq(int row,int col,int length,int combi) { if(length==8) { printf("%d\n",combi); return; } combi = (combi * 10) + a[row][col]; if((row-1)>=0) genSeq(row-1,col,length+1,combi); if((col-1)>=0) genSeq(row,col-1,length+1,combi); if((row+1)<6) genSeq(row+1,col,length+1,combi); if((col+1)<6) genSeq(row,col+1,length+1,combi); if((row+1)<6&&(col+1)<6) genSeq(row+1,col+1,length+1,combi); if((row-1)>=0&&(col+1)<6) genSeq(row-1,col+1,length+1,combi); if((row+1)<6&&(row-1)>=0) genSeq(row+1,col-1,length+1,combi); if((row-1)>=0&&(col-1)>=0) genSeq(row-1,col-1,length+1,combi); } I was also thinking of writing a dynamic program basically recursion with memorization. Is it a better choice?? if yes than I'm not clear how to implement it in recursion. Have i really hit a dead end with approach??? Thankyou Edit Eg result 12121212,12121218,12121219,12121211,12121213. the restrictions are that you have to move to your neighbor from any point, you have to start for each position in the matrix i.e each row,col. you can move one step at a time, i.e right, left, up, down and the both diagonal positions. Check the if conditions. i.e if your in (0,0) you can move to either (1,0) or (1,1) or (0,1) i.e three neighbors. if your in (2,2) you can move to eight neighbors. so on...

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• Haskell type classes and type families (cont'd)

  - by Giuseppe Maggiore

  I need some help in figuring a compiler error which is really driving me nuts... I have the following type class: infixl 7 --> class Selectable a s b where type Res a s b :: * (-->) :: (CNum n) => (Reference s a) -> (n,(a->b),(a->b->a)) -> Res a s b which I instance twice. First time goes like a charm: instance Selectable a s b where type Res a s b = Reference s b (-->) (Reference get set) (_,read,write) = (Reference (\s -> let (v,s') = get s in (read v,s')) (\s -> \x -> let (v,s') = get s v' = write v x (_,s'') = set s' v' in (x,s''))) since the type checker infers (-->) :: Reference s a -> (n,a->b,a->b->a) -> Reference s b and this signature matches with the class signature for (--) since Res a s b = Reference s b Now I add a second instance and everything breaks: instance (Recursive a, Rec a ~ reca) => Selectable a s (Method reca b c) where type Res a s (Method reca b c) = b -> Reference s c (-->) (Reference get set) (_,read,write) = \(x :: b) -> from_constant( Constant(\(s :: s)-> let (v,s') = get s :: (a,s) m = read v ry = m x :: Reference (reca) c (y,v') = getter ry (cons v) :: (c,reca) v'' = elim v' (_,s'') = set s' v'' in (y,s''))) :: Reference s c the compiler complains that Couldn't match expected type `Res a s (Method reca b c)' against inferred type `b -> Reference s c' The lambda expression `\ (x :: b) -> ...' has one argument, which does not match its type In the expression: \ (x :: b) -> from_constant (Constant (\ (s :: s) -> let ... in ...)) :: Reference s c In the definition of `-->': --> (Reference get set) (_, read, write) = \ (x :: b) -> from_constant (Constant (\ (s :: s) -> ...)) :: Reference s c reading carefully the compiler is telling me that it has inferred the type of (--) thusly: (-->) :: Reference s a -> (n,a->(Method reca b c),a->(Method reca b c)->a) -> (b -> Reference s c) which is correct since Res a s (Method reca b c) = b -> Reference s c but why can't it match the two definitions? Sorry for not offering a more succint and standalone example, but in this case I cannot figure how to do it...

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• Calculate minimum moves to solve a puzzle

  - by Luke

  I'm in the process of creating a game where the user will be presented with 2 sets of colored tiles. In order to ensure that the puzzle is solvable, I start with one set, copy it to a second set, then swap tiles from one set to another. Currently, (and this is where my issue lies) the number of swaps is determined by the level the user is playing - 1 swap for level 1, 2 swaps for level 2, etc. This same number of swaps is used as a goal in the game. The user must complete the puzzle by swapping a tile from one set to the other to make the 2 sets match (by color). The order of the tiles in the (user) solved puzzle doesn't matter as long as the 2 sets match. The problem I have is that as the number of swaps I used to generate the puzzle approaches the number of tiles in each set, the puzzle becomes easier to solve. Basically, you can just drag from one set in whatever order you need for the second set and solve the puzzle with plenty of moves left. What I am looking to do is after I finish building the puzzle, calculate the minimum number of moves required to solve the puzzle. Again, this is almost always less than the number of swaps used to create the puzzle, especially as the number of swaps approaches the number of tiles in each set. My goal is to calculate the best case scenario and then give the user a "fudge factor" (i.e. 1.2 times the minimum number of moves). Solving the puzzle in under this number of moves will result in passing the level. A little background as to how I currently have the game configured: Levels 1 to 10: 9 tiles in each set. 5 different color tiles. Levels 11 to 20: 12 tiles in each set. 7 different color tiles. Levels 21 to 25: 15 tiles in each set. 10 different color tiles. Swapping within a set is not allowed. For each level, there will be at least 2 tiles of a given color (one for each set in the solved puzzle). Is there any type of algorithm anyone could recommend to calculate the minimum number of moves to solve a given puzzle?

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• Avoiding explicit recursion in Haskell

  - by Travis Brown

  The following simple function applies a given monadic function iteratively until it hits a Nothing, at which point it returns the last non-Nothing value. It does what I need, and I understand how it works. lastJustM :: (Monad m) => (a -> m (Maybe a)) -> a -> m a lastJustM g x = g x >>= maybe (return x) (lastJustM g) As part of my self-education in Haskell I'm trying to avoid explicit recursion (or at least understand how to) whenever I can. It seems like there should be a simple non-explicitly recursive solution in this case, but I'm having trouble figuring it out. I don't want something like a monadic version of takeWhile, since it could be expensive to collect all the pre-Nothing values, and I don't care about them anyway. I checked Hoogle for the signature and nothing shows up. The m (Maybe a) bit makes me think a monad transformer might be useful here, but I don't really have the intuitions I'd need to come up with the details (yet). It's probably either embarrassingly easy to do this or embarrassingly easy to see why it can't or shouldn't be done, but this wouldn't be the first time I've used self-embarrassment as a pedagogical strategy. Background: Here's a simplified working example for context: suppose we're interested in random walks in the unit square, but we only care about points of exit. We have the following step function: randomStep :: (Floating a, Ord a, Random a) => a -> (a, a) -> State StdGen (Maybe (a, a)) randomStep s (x, y) = do (a, gen') <- randomR (0, 2 * pi) <$> get put gen' let (x', y') = (x + s * cos a, y + s * sin a) if x' < 0 || x' > 1 || y' < 0 || y' > 1 then return Nothing else return $ Just (x', y') Something like evalState (lastJustM (randomStep 0.01) (0.5, 0.5)) <$> newStdGen will give us a new data point.

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• Combining FileStream and MemoryStream to avoid disk accesses/paging while receiving gigabytes of data?

  - by w128

  I'm receiving a file as a stream of byte[] data packets (total size isn't known in advance) that I need to store somewhere before processing it immediately after it's been received (I can't do the processing on the fly). Total received file size can vary from as small as 10 KB to over 4 GB. One option for storing the received data is to use a MemoryStream, i.e. a sequence of MemoryStream.Write(bufferReceived, 0, count) calls to store the received packets. This is very simple, but obviously will result in out of memory exception for large files. An alternative option is to use a FileStream, i.e. FileStream.Write(bufferReceived, 0, count). This way, no out of memory exceptions will occur, but what I'm unsure about is bad performance due to disk writes (which I don't want to occur as long as plenty of memory is still available) - I'd like to avoid disk access as much as possible, but I don't know of a way to control this. I did some testing and most of the time, there seems to be little performance difference between say 10 000 consecutive calls of MemoryStream.Write() vs FileStream.Write(), but a lot seems to depend on buffer size and the total amount of data in question (i.e the number of writes). Obviously, MemoryStream size reallocation is also a factor. Does it make sense to use a combination of MemoryStream and FileStream, i.e. write to memory stream by default, but once the total amount of data received is over e.g. 500 MB, write it to FileStream; then, read in chunks from both streams for processing the received data (first process 500 MB from the MemoryStream, dispose it, then read from FileStream)? Another solution is to use a custom memory stream implementation that doesn't require continuous address space for internal array allocation (i.e. a linked list of memory streams); this way, at least on 64-bit environments, out of memory exceptions should no longer be an issue. Con: extra work, more room for mistakes. So how do FileStream vs MemoryStream read/writes behave in terms of disk access and memory caching, i.e. data size/performance balance. I would expect that as long as enough RAM is available, FileStream would internally read/write from memory (cache) anyway, and virtual memory would take care of the rest. But I don't know how often FileStream will explicitly access a disk when being written to. Any help would be appreciated.

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• Why did File::Find finish short of completely traversing a large directory?

  - by Stan

  A directory exists with a total of 2,153,425 items (according to Windows folder Properties). It contains .jpg and .gif image files located within a few subdirectories. The task was to move the images into a different location while querying each file's name to retrieve some relevant info and store it elsewhere. The script that used File::Find finished at 20462 files. Out of curiosity I wrote a tiny recursive function to count the items which returned a count of 1,734,802. I suppose the difference can be accounted for by the fact that it didn't count folders, only files that passed the -f test. The problem itself can be solved differently by querying for file names first instead of traversing the directory. I'm just wondering what could've caused File::Find to finish at a small fraction of all files. The data is stored on an NTFS file system. Here is the meat of the script; I don't think including DBI stuff would be relevant since I reran the script with nothing but a counter in process_img() which returned the same number. find(\&process_img, $path_from); sub process_img { eval { return if ($_ eq "." or $_ eq ".."); ## Omitted querying and composing new paths for brevity. make_path("$path_to\\img\\$dir_area\\$dir_address\\$type"); copy($File::Find::name, "$path_to\\img\\$dir_area\\$dir_address\\$type\\$new_name"); }; if ($@) { print STDERR "eval barks: $@\n"; return } } And here is another method I used to count files: count_images($path_from); sub count_images { my $path = shift; opendir my $images, $path or die "died opening $path"; while (my $item = readdir $images) { next if $item eq '.' or $item eq '..'; $img_counter++ && next if -f "$path/$item"; count_images("$path/$item") if -d "$path/$item"; } closedir $images or die "died closing $path"; } print $img_counter;

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• NSNotifications vs delegate for multiple instances of same protocol

  - by Brent Traut

  I could use some architectural advice. I've run into the following problem a few times now and I've never found a truly elegant way to solve it. The issue, described at the highest level possible:I have a parent class that would like to act as the delegate for multiple children (all using the same protocol), but when the children call methods on the parent, the parent no longer knows which child is making the call. I would like to use loose coupling (delegates/protocols or notifications) rather than direct calls. I don't need multiple handlers, so notifications seem like they might be overkill. To illustrate the problem, let me try a super-simplified example: I start with a parent view controller (and corresponding view). I create three child views and insert each of them into the parent view. I would like the parent view controller to be notified whenever the user touches one of the children. There are a few options to notify the parent: Define a protocol. The parent implements the protocol and sets itself as the delegate to each of the children. When the user touches a child view, its view controller calls its delegate (the parent). In this case, the parent is notified that a view is touched, but it doesn't know which one. Not good enough. Same as #1, but define the methods in the protocol to also pass some sort of identifier. When the child tells its delegate that it was touched, it also passes a pointer to itself. This way, the parent know exactly which view was touched. It just seems really strange for an object to pass a reference to itself. Use NSNotifications. The parent defines a separate method for each of the three children and then subscribes to the "viewWasTouched" notification for each of the three children as the notification sender. The children don't need to attach themselves to the user dictionary, but they do need to send the notification with a pointer to themselves as the scope. Same as #4, but rather than using separate methods, the parent could just use one with a switch case or other branching along with the notification's sender to determine which path to take. Create multiple man-in-the-middle classes that act as the delegates to the child views and then call methods on the parent either with a pointer to the child or with some other differentiating factor. This approach doesn't seem scalable. Are any of these approaches considered best practice? I can't say for sure, but it feels like I'm missing something more obvious/elegant.

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• Deleting a node in a family tree

  - by user559142

  Hi, I'm trying to calclulate the best way to delete a node in a family tree. First, a little description of how the app works. My app makes the following assumption: Any node can only have one partner. That means that any child a single node has, it will also be the partner nodes child too. Therefore, step relations, divorces etc aren't compensated for. A node always has two parents - A mother and father cannot be added seperately. If the user doesn't know the details - the nodes attributes are set to a default value. Also any node can add parents, siblings, children to itself. Therefore in law relationships can be added. I have the following classes: FamilyMember String fName; String lName; String dob; String gender; FamilyMember mother, father, partner; ArrayListchildren; int index; int generation; void linkParents(); void linkPartner(); void addChild(); //gets & sets for fields Family ArrayListfamily; void addMember(); void removeMember(); FamilyMember getFamilyMember(index); ArrayListgetFamilyMembers(); FamilyTree Family family; void removeMember(); //need help void displayFamilyMembers(); void addFamilyMember(); void enterDetails(); void displayAncestors(); void displayDescendants(); void printDescendants(); FamilyMember findRootNode(); void sortGenerations(); void getRootGeneration(); I am having trouble with identifying the logic for removing a member. All other functions work fine. Has anyone developed a family tree app before who knows how to deal with removing various different nodes in the family "tree"? e.g. removing a leaf removing a leaf with partner (what if partner has parents etc) removing a parent It seems to be another recursive property but my head is swelling from over thought.

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• color letters in a div

  - by Growler

  I've created a palindrome checker. I want to take it one step further and show the letters being compared as it is being checked. HTML: <p id="typing"></p> <input type="text" id="textBox" onkeyup="pal(this.value);" value="" /> <div id="response"></div> <hr> <div id="palindromeRun"></div> JS: To do this, I run the recursive check... Then if it is a palindrome, I run colorLetters(), which I'm trying to highlight in green each letter as it is being checked. Right now it is just rewriting palindromeRun's HTML with the first letter. I know this is because of the way I'm resetting its HTML. I don't know how to just grab the first and last letter, change only those letters' css, then increment i and j on the next setTimeout loop. var timeout2 = null; function pal (input) { var str = input.replace(/\s/g, ''); var str2 = str.replace(/\W/, ''); if (checkPal(str2, 0, str2.length-1)) { $("#textBox").css({"color" : "green"}); $("#response").html(input + " is a palindrome"); $("#palindromeRun").html(input); colorLetters(str2, 0, str2.length-1); } else { $("#textBox").css({"color" : "red"}); $("#response").html(input + " is not a palindrome"); } if (input.length <= 0) { $("#response").html(""); $("#textBox").css({"color" : "black"}); } } function checkPal (input, i, j) { if (input.length <= 1) { return false; } if (i === j || ((j-i) == 1 && input.charAt(i) === input.charAt(j))) { return true; } else { if (input.charAt(i).toLowerCase() === input.charAt(j).toLowerCase()) { return checkPal(input, ++i, --j); } else { return false; } } } function colorLetters(myinput, i, j) { if (timeout2 == null) { timeout2 = setTimeout(function () { console.log("called"); var firstLetter = $("#palindromeRun").html(myinput.charAt(i)) var secondLetter = $("#palindromeRun").html(myinput.charAt(j)) $(firstLetter).css({"color" : "red"}); $(secondLetter).css({"color" : "green"}); i++; j++; timeout2=null; }, 1000); } } Secondary: If possible, I'd just like to have it colors the letters as the user is typing... I realize this will require a setTimeout on each keyup, but also am not sure how to write this.

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• DFS Backtracking with java

  - by Cláudio Ribeiro

  I'm having problems with DFS backtracking in an adjacency matrix. Here's my code: (i added the test to the main in case someone wants to test it) public class Graph { private int numVertex; private int numEdges; private boolean[][] adj; public Graph(int numVertex, int numEdges) { this.numVertex = numVertex; this.numEdges = numEdges; this.adj = new boolean[numVertex][numVertex]; } public void addEdge(int start, int end){ adj[start-1][end-1] = true; adj[end-1][start-1] = true; } List<Integer> visited = new ArrayList<Integer>(); public Integer DFS(Graph G, int startVertex){ int i=0; if(pilha.isEmpty()) pilha.push(startVertex); for(i=1; i<G.numVertex; i++){ pilha.push(i); if(G.adj[i-1][startVertex-1] != false){ G.adj[i-1][startVertex-1] = false; G.adj[startVertex-1][i-1] = false; DFS(G,i); break; }else{ visited.add(pilha.pop()); } System.out.println("Stack: " + pilha); } return -1; } Stack<Integer> pilha = new Stack(); public static void main(String[] args) { Graph g = new Graph(6, 9); g.addEdge(1, 2); g.addEdge(1, 5); g.addEdge(2, 4); g.addEdge(2, 5); g.addEdge(2, 6); g.addEdge(3, 4); g.addEdge(3, 5); g.addEdge(4, 5); g.addEdge(6, 4); g.DFS(g, 1); } } I'm trying to solve the euler path problem. the program solves basic graphs but when it needs to backtrack, it just does not do it. I think the problem might be in the stack manipulations or in the recursive dfs call. I've tried a lot of things, but still can't seem to figure out why it does not backtrack. Can somebody help me ?

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• Is 4-5 years the “Midlife Crisis” for a programming career?

  - by Jeffrey

  I’ve been programming C# professionally for a bit over 4 years now. For the past 4 years I’ve worked for a few small/medium companies ranging from “web/ads agencies”, small industry specific software shops to a small startup. I've been mainly doing "business apps" that involves using high-level programming languages (garbage collected) and my overall experience was that all of the works I’ve done could have been more professional. A lot of the things were done incorrectly (in a rush) mainly due to cost factor that people always wanted something “now” and with the smallest amount of spendable money. I kept on thinking maybe if I could work for a bigger companies or a company that’s better suited for programmers, or somewhere that's got the money and time to really build something longer term and more maintainable I may have enjoyed more in my career. I’ve never had a “mentor” that guided me through my 4 years career. I am pretty much blog / google / self taught programmer other than my bachelor IT degree. I’ve also observed another issue that most so called “senior” programmer in “my working environment” are really not that senior skill wise. They are “senior” only because they’ve been a long time programmer, but the code they write or the decisions they make are absolutely rubbish! They don't want to learn, they don't want to be better they just want to get paid and do what they've told to do which make sense and most of us are like that. Maybe that’s why they are where they are now. But I don’t want to become like them I want to be better. I’ve run into a mental state that I no longer intend to be a programmer for my future career. I started to think maybe there are better things out there to work on. The more blogs I read, the more “best practices” I’ve tried the more I feel I am drifting away from “my reality”. But I am not a great programmer otherwise I don't think I am where I am now. I think 4-5 years is a stage that can be a step forward career wise or a step out of where you are. I just wanted to hear what other have to say about what I’ve mentioned above and whether you’ve experienced similar situation in your past programming career and how you dealt with it. Thanks.

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• synchronized in java - Proper use

  - by ZoharYosef

  I'm building a simple program to use in multi processes (Threads). My question is more to understand - when I have to use a reserved word synchronized? Do I need to use this word in any method that affects the bone variables? I know I can put it on any method that is not static, but I want to understand more. thank you! here is the code: public class Container { // *** data members *** public static final int INIT_SIZE=10; // the first (init) size of the set. public static final int RESCALE=10; // the re-scale factor of this set. private int _sp=0; public Object[] _data; /************ Constructors ************/ public Container(){ _sp=0; _data = new Object[INIT_SIZE]; } public Container(Container other) { // copy constructor this(); for(int i=0;i<other.size();i++) this.add(other.at(i)); } /** return true is this collection is empty, else return false. */ public synchronized boolean isEmpty() {return _sp==0;} /** add an Object to this set */ public synchronized void add (Object p){ if (_sp==_data.length) rescale(RESCALE); _data[_sp] = p; // shellow copy semantic. _sp++; } /** returns the actual amount of Objects contained in this collection */ public synchronized int size() {return _sp;} /** returns true if this container contains an element which is equals to ob */ public synchronized boolean isMember(Object ob) { return get(ob)!=-1; } /** return the index of the first object which equals ob, if none returns -1 */ public synchronized int get(Object ob) { int ans=-1; for(int i=0;i<size();i=i+1) if(at(i).equals(ob)) return i; return ans; } /** returns the element located at the ind place in this container (null if out of range) */ public synchronized Object at(int p){ if (p>=0 && p<size()) return _data[p]; else return null; }

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• Haskell Add Function Return to List Until Certain Length

  - by kienjakenobi

  I want to write a function which takes a list and constructs a subset of that list of a certain length based on the output of a function. If I were simply interested in the first 50 elements of the sorted list xs, then I would use fst (splitAt 50 (sort xs)). However, the problem is that elements in my list rely on other elements in the same list. If I choose element p, then I MUST also choose elements q and r, even if they are not in the first 50 elements of my list. I am using a function finderFunc which takes an element a from the list xs and returns a list with the element a and all of its required elements. finderFunc works fine. Now, the challenge is to write a function which builds a list whose total length is 50 based on multiple outputs of finderFunc. Here is my attempt at this: finish :: [a] -> [a] -> [a] --This is the base case, which adds nothing to the final list finish [] fs = [] --The function is recursive, so the fs variable is necessary so that finish -- can forward the incomplete list to itself. finish ps fs -- If the final list fs is too small, add elements to it | length fs < 50 && length (fs ++ newrs) <= 50 = fs ++ finish newps newrs -- If the length is met, then add nothing to the list and quit | length fs >= 50 = finish [] fs -- These guard statements are currently lacking, not the main problem | otherwise = finish [] fs where --Sort the candidate list sortedps = sort ps --(finderFunc a) returns a list of type [a] containing a and all the -- elements which are required to go with it. This is the interesting -- bit. rs is also a subset of the candidate list ps. rs = finderFunc (head sortedps) --Remove those elements which are already in the final list, because -- there can be overlap newrs = filter (`notElem` fs) rs --Remove the elements we will add to the list from the new list -- of candidates newps = filter (`notElem` rs) ps I realize that the above if statements will, in some cases, not give me a list of exactly 50 elements. This is not the main problem, right now. The problem is that my function finish does not work at all as I would expect it to. Not only does it produce duplicate elements in the output list, but it sometimes goes far above the total number of elements I want to have in the list. The way this is written, I usually call it with an empty list, such as: finish xs [], so that the list it builds on starts as an empty list.

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• Inbreeding-immune database structure

  - by Nick Savage

  I have an application that requires a "simple" family tree. I would like to be able to perform queries that will give me data for an entire family given one id from a member in the family. I say simple because it does not need to take into account adoption or any other obscurities. The requirements for the application are as follows: Any two people will not be able to breed if they're from the same genetic line Needs to allow for the addition of new family lines (new people with no previous family) Need to be able to pull siblings, parents separately through queries I'm having trouble coming up with the proper structure for the database. So far I've come up with two solutions but they're not very reliable and will probably get out of hand quite quickly. Solution 1 involves placing a family_ids field on the people table and storing a list of unique family ids. Each time two people breed the lists are checked against each other to make sure no ids match and if everything checks out will merge the two lists and set that as the child's family_ids field. Example: Father (family_ids: (null)) breeds with Mother (family_ids: (213, 519)) -> Child (family_ids: (213, 519)) breeds with Random Person (family_ids: (813, 712, 122, 767)) -> Grandchild (family_ids: (213, 519, 813, 712, 122, 767)) And so on and so forth... The problem I see with this is the lists becoming unreasonably large as time goes on. Solution 2 uses cakephp's associations to declare: public $belongsTo = array( 'Father' => array( 'className' => 'User', 'foreignKey' => 'father_id' ), 'Mother' => array( 'className' => 'User', 'foreignKey' => 'mother_id' ) ); Now setting recursive to 2 will fetch the results of the mother and father, along with their mother and father, and so on and so forth all the way down the line. The problem with this route is that the data is in nested arrays and I'm unsure of how to efficiently work through the code. If anyone would be able to steer me in the direction of the most efficient way to handle what I want to achieve that would be tremendously helpful. Any and all help is greatly appreciated and I'll gladly answer any questions anyone has. Thanks a lot.

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• Architectural Design for a Data-Driven Silverlight WP7 app

  - by Rosarch

  I have a Silverlight Windows Phone 7 app that pulls data from a public API. I find myself doing much of the same thing over and over again: In the UI, set a loading message or loading progress bar in place of where the content is Get the content, which may be already in memory, cached in isolated file storage, or require an HTTP request If the content can not be acquired (no network connection, etc), display an error message If the content is acquired, display it in the UI Keep the content in main memory for subsequent queries The content that is displayed to the user can be taken directly from a data source, such as an ObservableCollection, or it may be a query on a data source. I would like to factor out this repetitive process into a framework where ideally only the following needs to be specified: Where to display the content in the UI The UI elements to show while loading, on failure, and on success The URI of the HTTP request How to parse the HTTP response into the data structure that will kept in memory The location of the file in isolated storage, if it exists How to parse the file contents into the data structure that will be kept in memory It may sound like a lot, but two strings, three FrameworkElements, and two methods is less than the overhead that I currently have. Also, this needs to work for however the data is maintained in memory, and needs to work for direct collections and queries on those collections. My questions are: Has something like this already been implemented? Are my thoughts about the topic above fundamentally wrong in some way? Here is a design I'm thinking of: There are two components, a View and a Model. The View is given the FrameworkElements for loading, failure, and success. It is also given a reference to the corresponding Model. The View is a UserControl that is placed somewhere in the UI. The Model a class that is given the URI for the data, a method of how to parse the data, and optionally a filename and how to parse the file. It is responsible for retrieving the data and notifying the View whenever the current status (loading/fail/success) changes. If the data downloaded from the network is different from the cache, the network data takes precedence. When the app closes or is tombstoned, the model writes the data to the cache. How does that sound?

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• c++ recursion with arrays

  - by Sam

  I have this project that I'm working on for a class, and I'm not looking for the answer, but maybe just a few tips since I don't feel like I'm using true recursion. The problem involves solving the game of Hi Q or "peg solitaire" where you want the end result to be one peg remaining (it's played with a triangular board and one space is open at the start.) I've represented the board with a simple array, each index being a spot and having a value of 1 if it has a peg, and 0 if it doesn't and also the set of valid moves with a 2 dimensional array that is 36, 3 (each move set contains 3 numbers; the peg you're moving, the peg it hops over, and the destination index.) So my problem is that in my recursive function, I'm using a lot of iteration to determine things like which space is open (or has a value of 0) and which move to use based on which space is open by looping through the arrays. Secondly, I don't understand how you would then backtrack with recursion, in the event that an incorrect move was made and you wanted to take that move back in order to choose a different one. This is what I have so far; the "a" array represents the board, the "b" array represents the moves, and the "c" array was my idea of a reminder as to which moves I used already. The functions used are helper functions that basically just loop through the arrays to find an empty space and corresponding move. : void solveGame(int a[15], int b[36][3], int c[15][3]){ int empSpace; int moveIndex; int count = 0; if(pegCount(a) < 2){ return; } else{ empSpace = findEmpty(a); moveIndex = chooseMove( a, b, empSpace); a[b[moveIndex][0]] = 0; a[b[moveIndex][1]] = 0; a[b[moveIndex][2]] = 1; c[count][0] = b[moveIndex][0]; c[count][1] = b[moveIndex][1]; c[count][2] = b[moveIndex][2]; solveGame(a,b,c); } }

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• How do I go about link web content in a database with a nested set model?

  - by wb

  My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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• Sorting a list of numbers with modified cost

  - by David

  First, this was one of the four problems we had to solve in a project last year and I couldn’t find a suitable algorithm so we handle in a brute force solution. Problem: The numbers are in a list that is not sorted and supports only one type of operation. The operation is defined as follows: Given a position i and a position j the operation moves the number at position i to position j without altering the relative order of the other numbers. If i j, the positions of the numbers between positions j and i - 1 increment by 1, otherwise if i < j the positions of the numbers between positions i+1 and j decreases by 1. This operation requires i steps to find a number to move and j steps to locate the position to which you want to move it. Then the number of steps required to move a number of position i to position j is i+j. We need to design an algorithm that given a list of numbers, determine the optimal (in terms of cost) sequence of moves to rearrange the sequence. Attempts: Part of our investigation was around NP-Completeness, we make it a decision problem and try to find a suitable transformation to any of the problems listed in Garey and Johnson’s book: Computers and Intractability with no results. There is also no direct reference (from our point of view) to this kind of variation in Donald E. Knuth’s book: The art of Computer Programing Vol. 3 Sorting and Searching. We also analyzed algorithms to sort linked lists but none of them gives a good idea to find de optimal sequence of movements. Note that the idea is not to find an algorithm that orders the sequence, but one to tell me the optimal sequence of movements in terms of cost that organizes the sequence, you can make a copy and sort it to analyze the final position of the elements if you want, in fact we may assume that the list contains the numbers from 1 to n, so we know where we want to put each number, we are just concerned with minimizing the total cost of the steps. We tested several greedy approaches but all of them failed, divide and conquer sorting algorithms can’t be used because they swap with no cost portions of the list and our dynamic programing approaches had to consider many cases. The brute force recursive algorithm takes all the possible combinations of movements from i to j and then again all the possible moments of the rest of the element’s, at the end it returns the sequence with less total cost that sorted the list, as you can imagine the cost of this algorithm is brutal and makes it impracticable for more than 8 elements. Our observations: n movements is not necessarily cheaper than n+1 movements (unlike swaps in arrays that are O(1)). There are basically two ways of moving one element from position i to j: one is to move it directly and the other is to move other elements around i in a way that it reaches the position j. At most you make n-1 movements (the untouched element reaches its position alone). If it is the optimal sequence of movements then you didn’t move the same element twice.

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• passing back answers in prolog

  - by AhmadAssaf

  i have this code than runs perfectly .. returns a true .. when tracing the values are ok .. but its not returning back the answer .. it acts strangely when it ends and always return empty list .. uninstantiated variable .. test :- extend(4,12,[4,3,1,2],[[1,5],[3,4],[6]],_ExtendedBins). %printing basic information about the extend(NumBins,Capacity,RemainingNumbers,BinsSoFar,_ExtendedBins) :- getNumberofBins(BinsSoFar,NumberOfBins), msort(RemainingNumbers,SortedRemaining),nl, format("Current Number of Bins is :~w\n",[NumberOfBins]), format("Allowed Capacity is :~w\n",[Capacity]), format("maximum limit in bin is :~w\n",[NumBins]), format("Trying to fit :~w\n\n",[SortedRemaining]), format("Possible Solutions :\n\n"), fitElements(NumBins,NumberOfBins, Capacity,SortedRemaining,BinsSoFar,[]). %this is were the creation for possibilities will start %will check first if the number of bins allowed is less than then %we create a new list with all the possible combinations %after that we start matching to other bins with capacity constraint fitElements(NumBins,NumberOfBins, Capacity,RemainingNumbers,Bins,ExtendedBins) :- ( NumberOfBins < NumBins -> print('Creating new set: '); print('Sorry, Cannot create New Sets')), createNewList(Capacity,RemainingNumbers,Bins,ExtendedBins). createNewList(Capacity,RemainingNumbers,Bins,ExtendedBins) :- createNewList(Capacity,RemainingNumbers,Bins,[],ExtendedBins), print(ExtendedBins). createNewList(0,Bins,Bins,ExtendedBins,ExtendedBins). createNewList(_,[],_,ExtendedBins,ExtendedBins). createNewList(Capacity,[Element|Rest],Bins,Temp,ExtendedBins) :- conjunct_to_list(Element,ListedElement), append(ListedElement,Temp,NewList), sumlist(NewList,Sum), (Sum =< Capacity, append(ListedElement,ExtendedBins,Result); Capacity = 0), createNewList(Capacity,Rest,Bins,NewList,Result). fit(0,[],ExtendedBins,ExtendedBins). fit(Capacity,[Element|Rest],Bin,ExtendedBins) :- conjunct_to_list(Element,Listed), append(Listed,Bin,NewBin), sumlist(NewBin,Sum), (Sum =< Capacity -> fit(Capacity,Rest,NewBin,ExtendedBins); Capacity = 0, append(NewBin,ExtendedBins,NewExtendedBins), print(NewExtendedBins), fit(0,[],NewBin,ExtendedBins)). %get the number of bins provided getNumberofBins(List,NumberOfBins) :- getNumberofBins(List,0,NumberOfBins). getNumberofBins([],NumberOfBins,NumberOfBins). getNumberofBins([_List|Rest],TempCount,NumberOfBins) :- NewCount is TempCount + 1, %calculate the count getNumberofBins(Rest,NewCount,NumberOfBins). %recursive call %Convert set of terms into a list - used when needed to append conjunct_to_list((A,B), L) :- !, conjunct_to_list(A, L0), conjunct_to_list(B, L1), append(L0, L1, L). conjunct_to_list(A, [A]). Greatly appreciate the help

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• Please Describe Your Struggles with Minimizing Use of Global Variables

  - by MetaHyperBolic

  Most of the programs I write are relatively flowchartable processes, with a defined start and hoped-for end. The problems themselves can be complex but do not readily lean towards central use of objects and event-driven programming. Often, I am simply churning through great varied batches of text data to produce different text data. Only occasionally do I need to create a class: As an example, to track warnings, errors, and debugging message, I created a class (Problems) with one instantiation (myErr), which I believe to be an example of the Singleton design pattern. As a further factor, my colleagues are more old school (procedural) than I and are unacquainted with object-oriented programming, so I am loath to create things they could not puzzle through. And yet I hear, again and again, how even the Singleton design pattern is really an anti-pattern and ought to be avoided because Global Variables Are Bad. Minor functions need few arguments passed to them and have no need to know of configuration (unchanging) or program state (changing) -- I agree. However, the functions in the middle of the chain, which primarily control program flow, have a need for a large number of configuration variables and some program state variables. I believe passing a dozen or more arguments along to a function is a "solution," but hardly an attractive one. I could, of course, cram variables into a single hash/dict/associative array, but that seems like cheating. For instance, connecting to the Active Directory to make a new account, I need such configuration variables as an administrative username, password, a target OU, some default groups, a domain, etc. I would have to pass those arguments down through a variety of functions which would not even use them, merely shuffle them off down through a chain which would eventually lead to the function that actually needs them. I would at least declare the configuration variables to be constant, to protect them, but my language of choice these days (Python) provides no simple manner to do this, though recipes do exist as workarounds. Numerous Stack Overflow questions have hit on the why? of the badness and the requisite shunning, but do not often mention tips on living with this quasi-religious restriction. How have you resolved, or at least made peace with, the issue of global variables and program state? Where have you made compromises? What have your tricks been, aside from shoving around flocks of arguments to functions?

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