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• In R, how do you get the best fitting equation to a set of data?

  - by Matherion

  I'm not sure wether R can do this (I assume it can, but maybe that's just because I tend to assume that R can do anything :-)). What I need is to find the best fitting equation to describe a dataset. For example, if you have these points: df = data.frame(x = c(1, 5, 10, 25, 50, 100), y = c(100, 75, 50, 40, 30, 25)) How do you get the best fitting equation? I know that you can get the best fitting curve with: plot(loess(df$y ~ df$x)) But as I understood you can't extract the equation, see Loess Fit and Resulting Equation. When I try to build it myself (note, I'm not a mathematician, so this is probably not the ideal approach :-)), I end up with smth like: y.predicted = 12.71 + ( 95 / (( (1 + df$x) ^ .5 ) / 1.3)) Which kind of seems to approximate it - but I can't help to think that smth more elegant probably exists :-) I have the feeling that fitting a linear or polynomial model also wouldn't work, because the formula seems different from what those models generally use (i.e. this one seems to need divisions, powers, etc). For example, the approach in Fitting polynomial model to data in R gives pretty bad approximations. I remember from a long time ago that there exist languages (Matlab may be one of them?) that do this kind of stuff. Can R do this as well, or am I just at the wrong place? (Background info: basically, what we need to do is find an equation for determining numbers in the second column based on the numbers in the first column; but we decide the numbers ourselves. We have an idea of how we want the curve to look like, but we can adjust these numbers to an equation if we get a better fit. It's about the pricing for a product (a cheaper alternative to current expensive software for qualitative data analysis); the more 'project credits' you buy, the cheaper it should become. Rather than forcing people to buy a given number (i.e. 5 or 10 or 25), it would be nicer to have a formula so people can buy exactly what they need - but of course this requires a formula. We have an idea for some prices we think are ok, but now we need to translate this into an equation.

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• I have to do two seemingly mutually exclusive things on leaving an asp:textbox. Please help me get

  - by aape

  This project has gone from being a simple '99 Ford F-150 to the Homer. I've got controls with a gridview with textboxes for data entry. All the user controls on the pages are in AJAX updatepanels. User types in a database column or budget entity or some other financial thing they want to include in the report. The textboxes in the gridview have autopostback = true set. overly long background info When the user leaves the textbox, during the postback (triggered by onTextChanged) I do some validation back on the server on their entry - regexs, do they have rights to that column, is that column locked, etc. If it fails, I put a error message next to the textbox. If it passes, I wipe out any title or error that used to be next to the code. Focus is getting lost from the postback if they're tabbing out of the box, rather than going to the next textbox in the gridview. So to fix that I need, if their leaving the tb via the tab key, to also figure out what textbox or gridviewrow they're on, if they're not on the last row, and after the validation and labeling, put the focus on the textbox in the next row. I can't figure out how, in ontextchanged, to find what caused me to leave the textbox, so I'm thinking use javascript onkeyup to test the key pressed and then find the next box etc, but the ontextchanged fires first and then the js never does, and also, since the control is all AJAXed, the javascript can't find the textboxes because when you enter the page everything is collapsed (the requirements people loooove to collapse and expand things), and so when it's expanded, all the 'new' textboxes are up in the viewstate stuff in the page source, and not down where javascript can see them. The questions So I'm wondering if I can have an onblur in the javascript that can trigger a postback where I can do my validation and such, and either 1) include the keypressed or pick it out of sender in the event or 2) followup the onblur with onkeyup and somehow figure out what textbox is next on the grid and throw focus there. Or, is there another .NET based approach that could work for this? In terms of tearing the whole thing down and starting from scratch, I couldn't sell that to the bosses, I'm past the point of no return as far as that goes.

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• php regex guitar tab (tabs or tablature, a type of music notation)

  - by John

  I am in the process of creating a guitar tab to rtttl (Ring Tone Text Transfer Language) converter in PHP. In order to prepare a guitar tab for rtttl conversion I first strip out all comments (comments noted by #- and ended with -#), I then have a few lines that set tempo, note the tunning and define multiple instruments (Tempo 120\nDefine Guitar 1\nDefine Bass 1, etc etc) which are stripped out of the tab and set aside for later use. Now I essentially have nothing left except the guitar tabs. Each tab is prefixed with it's instrument name in conjunction with the instrument name noted prior. Some times we have tabs for 2 separate instruments that are linked because they are to be played together, ie a Guitar and a Bass Guitar playing together. Example 1, Standard Guitar Tab: |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| Example 2, Conjunction Tab: |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| | | |Bass 1 G|----------0-------0-----------0-------0--------| D|--------2-----------2-------2-----------2------| A|------3---------------3---3---------------3----| E|----3-------------------3-------------------3--| I have considered other methods of identifying the tabs with no solid results. I am hoping that someone who does regular expressions could help me find a way to identify a single guitar tab and if possible also be able to match a tab with multiple instruments linked together. Once the tabs are in an array I will go through them one line at a time and convert them into rtttl lines (exploded at each new line "\n"). I do not want to separate the guitar tabs in the document via explode "\n\n" or something similar because it does not identify the guitar tab, rather, it is identifying the space between the tabs - not on the tabs themselves. I have been messing with this for about a week now and this is the only major hold up I have. Everything else is fairly simple. As of current, I have tried many variations of the regex pattern. Here is one of the most recent test samples: <?php $t = " |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| | | |Bass 1 G|----------0-------0-----------0-------0--------| D|--------2-----------2-------2-----------2------| A|------3---------------3---3---------------3----| E|----3-------------------3-------------------3--| "; preg_match_all("/^.*?(\\|).*?(\\|)/is",$t,$p); print_r($p); ?> It is also worth noting that inside the tabs, where the dashes and #'s are, you may also have any variation of letters, numbers and punctuation. The beginning of each line marks the tuning of each string with one of the following case insensitive: a,a#,b,c,c#,d,d#,e,f,f#,g or g. Thanks in advance for help with this most difficult problem.

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• asp.net Wizard control strange issue

  - by epitka

  Update: There was actually a hidden panel with validator in the user control that was causing page not to be valid on the first postback. Consider this issue resolved. This is first time I am using this control and it is behaving rather strange. I have to click on the "Next" button twice for it to move to the next step. I tried explicitly setting active index, using MoveTo etc. Nothing works. Here is the markup for the control. Anybody has any ideas why? <asp:Wizard ID="UserWizard" runat="server" ActiveStepIndex="0" StartNextButtonImageUrl = "~/App_Themes/Default/images/buttons/continue.gif" StartNextButtonType="Image" StepNextButtonType="Image" StepNextButtonImageUrl="~/App_Themes/Default/images/buttons/continue.gif" FinishPreviousButtonImageUrl="~/App_Themes/Default/images/buttons/back.gif" FinishPreviousButtonType="Image" FinishCompleteButtonImageUrl="~/App_Themes/Default/images/buttons/save.gif" FinishCompleteButtonType="Image" CancelButtonType="Image" CancelButtonImageUrl="~/App_Themes/Default/images/buttons/back.gif" DisplaySideBar="false" > <WizardSteps> <asp:WizardStep Title="User Profile" ID="UserProfile" runat="server"> <uhc:ctlUserProfileEdit ID="ctlUserProfileEdit" runat="server"> </uhc:ctlUserProfileEdit> <br clear="all" /> <div> <asp:ImageButton ID="cmdResetPassword" runat="server" ImageUrl="~/App_Themes/Default/images/buttons/resetpassword.gif" /> </div> <div> <asp:UpdatePanel ID="upSchools" runat="server" ChildrenAsTriggers="true"> <ContentTemplate> <uhc:ctlSchoolLocationSelector ID="ctlSchoolLocationSelector" runat="server" /> </ContentTemplate> </asp:UpdatePanel> </div> </asp:WizardStep> <asp:WizardStep Title="Roles" ID="Roles" runat="server"> <uhc:ctlPermissionInternal ID="ctlPermissionInternal1" runat="server"></uhc:ctlPermissionInternal> <uhc:ctlPermissionExternal ID="ctlPermissionExternal1" runat="server"></uhc:ctlPermissionExternal> </asp:WizardStep> </WizardSteps> </asp:Wizard>

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• Dynamic Dispatch without Virtual Functions

  - by Kristopher Johnson

  I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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• Is MySQL Replication Appropriate in this case?

  - by MJB

  I have a series of databases, each of which is basically standalone. It initially seemed like I needed a replication solution, but the more I researched it, the more it felt like replication was overkill and not useful anyway. I have not done MySQL replication before, so I have been reading up on the online docs, googling, and searching SO for relevant questions, but I can't find a scenario quite like mine. Here is a brief description of my issue: The various databases almost never have a live connection to each other. They need to be able to "sync" by copying files to a thumb drive and then moving them to the proper destination. It is OK for the data to not match exactly, but they should have the same parent-child relationships. That is, if a generated key differs between databases, no big deal. But the visible data must match. Timing is not critical. Updates can be done a week later, or even a month later, as long as they are done eventually. Updates cannot be guaranteed to be in the proper order, or in any order for that matter. They will be in order from each database; just not between databases. Rather than a set of master-slave relationships, it is more like a central database (R/W) and multiple remote databases (also R/W). I won't know how many remote databases I have until they are created. And the central DB won't know that a database exists until data arrives from it. (To me, this implies I cannot use the method of giving each its own unique identity range to guarantee uniqueness in the central database.) It appears to me that the bottom line is that I don't want "replication" so much as I want "awareness". I want the central database to know what happened in the remote databases, but there is no time requirement. I want the remote databases to be aware of the central database, but they don't need to know about each other. WTH is my question? It is this: Does this scenario sound like any of the typical replication scenarios, or does it sound like I have to roll my own? Perhaps #7 above is the only one that matters, and given that requirement, out-of-the-box replication is impossible. EDIT: I realize that this question might be more suited to ServerFault. I also searched there and found no answers to my questions. And based on the replication questions I did find both on SO and SF, it seemed that the decision was 50-50 over where to put my question. Sorry if I guessed wrong.

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• Is a Multi-DAL Approach the way to go here?

  - by Krisc

  Working on the data access / model layer in this little MVC2 project and trying to think things out to future projects. I have a database with some basic tables and I have classes in the model layer that represent them. I obviously need something to connect the two. The easiest is to provide some sort of 'provider' that can run operations on the database and return objects. But this is for a website that would potentially be used "a lot" (I know, very general) so I want to cache results from the data layer and keep the cache updated as new data is generated. This question deals with how best to approach this problem of dual DALS. One that returns cached data when possible and goes to the data layer when there is a cache miss. But more importantly, how to integrate the core provider (thing that goes into database) with the caching layer so that it too can rely on cached objects rather than creating new ones. Right now I have the following interfaces: IDataProvider is used to reach the database. It doesn't concern itself with the meaning of the objects it produces, but simply the way to produce them. interface IDataProvider{ // Select, Update, Create, et cetera access IEnumerable<Entry> GetEntries(); Entry GetEntryById(int id); } IDataManager is a layer that sits on top of the IDataProvider layer and manages the cache interface IDataManager : IDataProvider{ void ClearCache(); } Note that in practice the IDataManager implementation will have useful helper functions to add objects to their related cache stores. (In the future I may define other functions on the interface) I guess what I am looking for is the best way to approach a loop back from the IDataProvider implementations so that they can access the cache. Or a different approach entirely may be in order? I am not very interested in 3rd party products at the moment as I am interested in the design of these things much more than this specific implementation. Edit: I realize the title may be a bit misleading. I apologize for that... not sure what to call this question.

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• Getting up to speed on modern architecture

  - by Matt Thrower

  Hi, I don't have any formal qualifications in computer science, rather I taught myself classic ASP back in the days of the dotcom boom and managed to get myself a job and my career developed from there. I was a confident and, I think, pretty good programmer in ASP 3 but as others have observed one of the problems with classic ASP was that it did a very good job of hiding the nitty-gritty of http so you could become quite competent as a programmer on the basis of relatively poor understanding of the technology you were working with. When I changed on to .NET at first I treated it like classic ASP, developing stand-alone applications as individual websites simply because I didn't know any better at the time. I moved jobs at this point and spent the next several years working on a single site whose architecture relied heavily on custom objects: in other words I gained a lot of experience working with .NET as a middle-tier development tool using a quite old-fashioned approach to OO design along the lines of the classic "car" class example that's so often used to teach OO. Breaking down programs into blocks of functionality and basing your classes and methods around that. Although we worked under an Agile approach to manage the work the whole setup was classic client/server stuff. That suited me and I gradually got to grips with .NET and started using it far more in the manner that it should be, and I began to see the power inherent in the technology and precisely why it was so much better than good old ASP 3. In my latest job I have found myself suddenly dropped in at the deep end with two quite young, skilled and very cutting-edge programmers. They've built a site architecture which is modelling along a lot of stuff which is new to me and which, in truth I'm having a lot of trouble understanding. The application is built on a cloud computing model with multi-tenancy and the architecture is all loosely coupled using a lot of interfaces, factories and the like. They use nHibernate a lot too. Shortly after I joined, both these guys left and I'm now supposedly the senior developer on a system whose technology and architecture I don't really understand and I have no-one to ask questions of. Except you, the internet. Frankly I feel like I've been pitched in at the deep end and I'm sinking. I'm not sure if this is because I lack the educational background to understand this stuff, if I'm simply not mathematically minded enough for modern computing (my maths was never great - my approach to design is often to simply debug until it works, then refactor until it looks neat), or whether I've simply been presented with too much of too radical a nature at once. But the only way to find out which it is is to try and learn it. So can anyone suggest some good places to start? Good books, tutorials or blogs? I've found a lot of internet material simply presupposes a level of understanding that I just don't have. Your advice is much appreciated. Help a middle-aged, stuck in the mud developer get enthusastic again! Please!

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• How can I link axes of imshow plots for zooming and panning?

  - by Adam Fraser

  Suppose I have a figure canvas with 3 plots... 2 are images of the same dimensions plotted with imshow, and the other is some other kind of subplot. I'd like to be able to link the x and y axes of the imshow plots so that when I zoom in one (using the zoom tool provided by the NavigationToolbar), the other zooms to the same coordinates, and when I pan in one, the other pans as well. Subplot methods such as scatter and histogram can be passed kwargs specifying an axes for sharex and sharey, but imshow has no such configuration. I started hacking my way around this by subclassing NavigationToolbar2WxAgg (shown below)... but there are several problems here. 1) This will link the axes of all plots in a canvas since all I've done is get rid of the checks for a.in_axes() 2) This worked well for panning, but zooming caused all subplots to zoom from the same global point, rather than from the same point in each of their respective axes. Can anyone suggest a workaround? Much thanks! -Adam from matplotlib.backends.backend_wxagg import NavigationToolbar2WxAgg class MyNavToolbar(NavigationToolbar2WxAgg): def __init__(self, canvas, cpfig): NavigationToolbar2WxAgg.__init__(self, canvas) # overrided # As mentioned in the code below, the only difference here from overridden # method is that this one doesn't check a.in_axes(event) when deciding which # axes to start the pan in... def press_pan(self, event): 'the press mouse button in pan/zoom mode callback' if event.button == 1: self._button_pressed=1 elif event.button == 3: self._button_pressed=3 else: self._button_pressed=None return x, y = event.x, event.y # push the current view to define home if stack is empty if self._views.empty(): self.push_current() self._xypress=[] for i, a in enumerate(self.canvas.figure.get_axes()): # only difference from overridden method is that this one doesn't # check a.in_axes(event) if x is not None and y is not None and a.get_navigate(): a.start_pan(x, y, event.button) self._xypress.append((a, i)) self.canvas.mpl_disconnect(self._idDrag) self._idDrag=self.canvas.mpl_connect('motion_notify_event', self.drag_pan) # overrided def press_zoom(self, event): 'the press mouse button in zoom to rect mode callback' if event.button == 1: self._button_pressed=1 elif event.button == 3: self._button_pressed=3 else: self._button_pressed=None return x, y = event.x, event.y # push the current view to define home if stack is empty if self._views.empty(): self.push_current() self._xypress=[] for i, a in enumerate(self.canvas.figure.get_axes()): # only difference from overridden method is that this one doesn't # check a.in_axes(event) if x is not None and y is not None and a.get_navigate() and a.can_zoom(): self._xypress.append(( x, y, a, i, a.viewLim.frozen(), a.transData.frozen())) self.press(event)

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• C# Type Casting at Runtimefor Array.SetValue

  - by sprocketonline

  I'm trying to create an array using reflection, and insert values into it. I'm trying to do this for many different types so would like a createAndFillArray function capable of this : Type t1 = typeof(A); Type t2 = typeof(B); double exampleA = 22.5; int exampleB = 43; Array arrA = createAndFillArray(t1, exampleA); Array arrB = createAndFillArray(t2, exampleB); private Array createAndFillArray(Type t, object val){ Array arr = Array.CreateInstance( t, 1); //length 1 in this example only, real-world is of variable length. arr.SetValue( val, 0 ); //this causes the following error: "System.InvalidCastException : Object cannot be stored in an array of this type." return arr; } with the class A being as follows: public class A{ public A(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator A(double d){ A a = new A(); a.Value = d; return a; } } and class B being very similar, but with int: public class B{ public B(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator B(double d){ B b = new B(); b.Value = d; return b; } } I hoped that the implicit operator would have ensured that the double be converted to class A, or the int to class B, and the error avoided; but this is obviously not so. The above is used in a custom deserialization class, which takes data from a custom data format and fills in the corresponding .Net object properties. I'm doing this via reflection and at runtime, so I think both are unavoidable. I'm targeting the C# 2.0 framework. I've dozens, if not hundreds, of classes similar to A and B, so would prefer to find a solution which improved on the createAndFillArray method rather than a solution which altered these classes.

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• Webservice for uploading data: security considerations

  - by Philip Daubmeier

  Hi everyone! Im not sure about what authentification method I should use for my webservice. I've searched on SO, and found nothing that helped me. Preliminary Im building an application that uploads data from a local database to a server (running my webservice), where all records are merged and stored in a central database. I am currently binary serializing a DataTable, that holds a small fragment of the local database, where all uninteresting stuff is already filtered out. The byte[] (serialized DataTable), together with the userid and a hash of the users password is then uploaded to the webservice via SOAP. The application together with the webservice already work exactly like intended. The Problem The issue I am thinking about is now: What is if someone just sniffs the network traffic, 'steals' the users id and password hash to send his own SOAP message with modified data that corrupts my database? Options The approaches to solving that problem, I already thought of, are: Using ssl + certificates for establishing the connection: I dont really want to use ssl, I would prefer a simpler solution. After all, every information that is transfered to the webservice can be seen on the website later on. What I want to say is: there is no secret/financial/business-critical information, that has to be hidden. I think ssl would be sort of an overkill for that task. Encrypting the byte[]: I think that would be a performance killer, considering that the goal of the excercise was simply to authenticate the user. Hashing the users password together with the data: I kind of like the idea: Creating a checksum from the data, concatenating that checksum with the password-hash and hashing this whole thing again. That would assure the data was sent from this specific user, and the data wasnt modified. The actual question So, what do you think is the best approach in terms of meeting the following requirements? Rather simple solution (As it doesnt have to be super secure; no secret/business-critical information transfered) Easily implementable retrospectively (Dont want to write it all again :) ) Doesnt impact to much on performance What do you think of my prefered solution, the last one in the list above? Is there any alternative solution I didnt mention, that would fit better? You dont have to answer every question in detail. Just push me in the right direction. I very much appreciate every well-grounded opinion. Thanks in advance!

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• how to add a dynamic param

  - by user569846

  the jquery plugin that im using is this http://code.google.com/p/jquery-in-place-editor/ if i have a table like this <table> <thead> <tr> <th>id</th> <th>first name </th> <th>last name </th> </tr> </thead> <tbody> <tr> <td class="id">1</td> <td class="fname">sarmen</td> <td class="lname">mikey</td> </tr> <tr> <td class="id">2</td> <td class="fname">john</td> <td class="lname">angelo</td> </tr> <tr> <td class="id">3</td> <td class="fname">sarmen</td> <td class="lname">grande</td> </tr> </tbody> </table> and my js looked something like this $("td.fname").editInPlace({ url: 'ajax.php', params: '', show_buttons: true }); then lets say i click on the first record to edit it which is fname of sarmen. how can i pass a param that only accociates id 1 ? because if i do a query of lets say "update tbl_users set fname = '$_POST['update_value']' where fname = '$_POST['original_html']'" (note: im just showing an example so no need to clean posts if that was bothering you :) ) if i run this query the fname of sarmen will update in two records rather than one. How can i only update to id of 1 being to update only one record.

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• Project Euler #18 - how to brute force all possible paths in tree-like structure using Python?

  - by euler user

  Am trying to learn Python the Atlantic way and am stuck on Project Euler #18. All of the stuff I can find on the web (and there's a LOT more googling that happened beyond that) is some variation on 'well you COULD brute force it, but here's a more elegant solution'... I get it, I totally do. There are really neat solutions out there, and I look forward to the day where the phrase 'acyclic graph' conjures up something more than a hazy, 1 megapixel resolution in my head. But I need to walk before I run here, see the state, and toy around with the brute force answer. So, question: how do I generate (enumerate?) all valid paths for the triangle in Project Euler #18 and store them in an appropriate python data structure? (A list of lists is my initial inclination?). I don't want the answer - I want to know how to brute force all the paths and store them into a data structure. Here's what I've got. I'm definitely looping over the data set wrong. The desired behavior would be to go 'depth first(?)' rather than just looping over each row ineffectually.. I read ch. 3 of Norvig's book but couldn't translate the psuedo-code. Tried reading over the AIMA python library for ch. 3 but it makes too many leaps. triangle = [ [75], [95, 64], [17, 47, 82], [18, 35, 87, 10], [20, 4, 82, 47, 65], [19, 1, 23, 75, 3, 34], [88, 2, 77, 73, 7, 63, 67], [99, 65, 4, 28, 6, 16, 70, 92], [41, 41, 26, 56, 83, 40, 80, 70, 33], [41, 48, 72, 33, 47, 32, 37, 16, 94, 29], [53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14], [70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57], [91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48], [63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31], [04, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23], ] def expand_node(r, c): return [[r+1,c+0],[r+1,c+1]] all_paths = [] my_path = [] for i in xrange(0, len(triangle)): for j in xrange(0, len(triangle[i])): print 'row ', i, ' and col ', j, ' value is ', triangle[i][j] ??my_path = somehow chain these together??? if my_path not in all_paths all_paths.append(my_path) Answers that avoid external libraries (like itertools) preferred.

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• c++ std::ostringstream vs std::string::append

  - by NickSoft

  In all examples that use some kind of buffering I see they use stream instead of string. How is std::ostringstream and << operator different than using string.append. Which one is faster and which one uses less resourses (memory). One difference I know is that you can output different types into output stream (like integer) rather than the limited types that string::append accepts. Here is an example: std::ostringstream os; os << "Content-Type: " << contentType << ";charset=" << charset << "\r\n"; std::string header = os.str(); vs std::string header("Content-Type: "); header.append(contentType); header.append(";charset="); header.append(charset); header.append("\r\n"); Obviously using stream is shorter, but I think append returns reference to the string so it can be written like this: std::string header("Content-Type: "); header.append(contentType) .append(";charset=") .append(charset) .append("\r\n"); And with output stream you can do: std::string content; ... os << "Content-Length: " << content.length() << "\r\n"; But what about memory usage and speed? Especially when used in a big loop. Update: To be more clear the question is: Which one should I use and why? Is there situations when one is preferred or the other? For performance and memory ... well I think benchmark is the only way since every implementation could be different. Update 2: Well I don't get clear idea what should I use from the answers which means that any of them will do the job, plus vector. Cubbi did nice benchmark with the addition of Dietmar Kühl that the biggest difference is construction of those objects. If you are looking for an answer you should check that too. I'll wait a bit more for other answers (look previous update) and if I don't get one I think I'll accept Tolga's answer because his suggestion to use vector is already done before which means vector should be less resource hungry.

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• Getting HIERARCHY_REQUEST_ERR when using Javascript to recursively generate a nested list

  - by Mark

  I have a method that is trying to take in a list. This list can contain data and other lists. The end goal is to try to convert something like this ["a", "b", ["c", "d"]] into <ol> <li> <b>a</a> </li> <li> <b>b</a> </li> <ol> <li> <b>c</a> </li> <li> <b>d</a> </li> </ol> </ol> The code is: function $(tagName) { return document.createElement(tagName); } //returns an html element representing data //data should be an array or some sort of value function tagMaker(data) { tag = null; if(data instanceof Array) { //data is an array, represent using <ol> tag = $("ol"); for(i=0; i<data.length; i++) { //construct one <li> for each item in the array listItem = $("li"); //get the html element representing this particular item in the array child = tagMaker(data[i]); //<li>*html for child*</li> listItem.appendChild(child); //add this item to the list tag.appendChild(listItem); } } else { //data is not an array, represent using <b>data</b> tag = $("b"); tag.innerHTML = data.toString(); } return tag; } Calling tagMaker throws HIERARCHY_REQUEST_ERR: DOM Exception 3, rather than generating a helpful HTML element object which I was planning to append to document.body.

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• Database Schema Versioning Strategies

  - by Jack Ryan

  I work on a project that uses a reasonably large database, the live version weighing in at somewhere around 60-80GB. The live database is the only real definitive source of our schema, and because of its size duplicating this database is too slow to be done often. This means we have ended up developing our database schema in a pretty ad hoc way, using sql compare to migrate changes from dev dbs to the live system, and only wiping our dev dbs every month or two. I am hoping to get some pointers on how to improve our database development work flow so that we have a little more control. Some things to think about: Currently nobody is really in charge of the database schema, all developers can change it if they need to, though generally these decisions are talked about before they are done. There are stored procedures, functions, and views in the database. These should probably be dumped to files so they can be reloaded on every build. Schema changes should probably be checked in as scripts. We have started to do this recently. However all our scripts must then be numbered (because there may be dependencies between them), and must be re runnable (because our build script currently runs them all in order). This makes them hard to read because they are full of conditionals that check whether tables or columns already exist. This is a step that is often forgotten by developers. Getting a new database should be quick and easy. This is currently a big problem, it takes several hours to get a copy of last nights backup and restore it onto a dev machine. Some mechanism needs to be in place to allow developers to update static data. We have tables that contain data that is never updated through the application, but does potentially need to be changed when we do a new release (often this drives dropdowns). The whole thing needs to be runnable as part of a build script. Are there any tools that can be used to help to do this? Eventually I would like to be at a point where a new DB can be built from scratch without copying any data from the live system. I don't mind writing some scripts to glue all the steps together but each part should be easily editable so that we continue to use it rather than make changes directly on DBs.

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• C++ Stack Overflow

  - by PhilMAN

  Here is some code: void main() { GameEngine ge("phil", "anotherguy"); string response; do { ge.playGame(); cout << endl << "Do you want to (r)eplay the same battle, (s)tart a new battle, or (q)uit? "; cin >> response; } while(response == "r" || response == "R" || response == "s" || response == "S" ); } GameEngine::GameEngine(string name1, string name2) { p1Name = name1; p2Name = name2; } void GameEngine::playGame() { cout << "PLAY GAME" << endl; Army p1, p2; Battlefield testField; RuleSet rs; int xSize = 13; // Number of rows int ySize = 13; // Number of columns loadData(p1, p2, testField, rs, xSize, ySize); ... } void GameEngine::loadData(Army& p1, Army& p2, Battlefield& testField, RuleSet& rs, int& xSize, int& ySize) { string terrain = BattlefieldUtils::pickTerrain(); string armySplit[14];//id index 1 string ruleSplit[19];//in index 7 string armyP1, armyP2, ruleSet; Skill p1Skills[8]; Skill p2Skills[8]; CreatureStack p1Stacks[20]; CreatureStack p2Stacks[20]; ... } CreatureStack(){quantity = 0; isLive = false; id = -1;}; Army(){}; Battlefield(){}; RuleSet(){}; I have posted every line of code that executes until the program crashes. This code ran fine for a long time, I added some stuff that does not even execute until way after the code I have posted here, and bam stack overflow that occurs at GameEngine::loadData() line: CreatureStack p2Stacks[20]; will not go away. What am I doing wrong here? Is that all the stack can handle? I increased the stack size in Visual Studio and got the error to go away, but that slowed things down considerably, so I would rather just get to the source of the issue and fix that.

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• How can I store large amount of data from a database to XML (speed problem, part three)?

  - by Andrija

  After getting some responses, the current situation is that I'm using this tip: http://www.ibm.com/developerworks/xml/library/x-tipbigdoc5.html (Listing 1. Turning ResultSets into XML), and XMLWriter for Java from http://www.megginson.com/downloads/ . Basically, it reads date from the database and writes them to a file as characters, using column names to create opening and closing tags. While doing so, I need to make two changes to the input stream, namely to the dates and numbers. // Iterate over the set while (rs.next()) { w.startElement("row"); for (int i = 0; i < count; i++) { Object ob = rs.getObject(i + 1); if (rs.wasNull()) { ob = null; } String colName = meta.getColumnLabel(i + 1); if (ob != null ) { if (ob instanceof Timestamp) { w.dataElement(colName, Util.formatDate((Timestamp)ob, dateFormat)); } else if (ob instanceof BigDecimal){ w.dataElement(colName, Util.transformToHTML(new Integer(((BigDecimal)ob).intValue()))); } else { w.dataElement(colName, ob.toString()); } } else { w.emptyElement(colName); } } w.endElement("row"); } The SQL that gets the results has the to_number command (e.g. to_number(sif.ID) ID ) and the to_date command (e.g. TO_DATE (sif.datum_do, 'DD.MM.RRRR') datum_do). The problems are that the returning date is a timestamp, meaning I don't get 14.02.2010 but rather 14.02.2010 00:00:000 so I have to format it to the dd.mm.yyyy format. The second problem are the numbers; for some reason, they are in database as varchar2 and can have leading zeroes that need to be stripped; I'm guessing I could do that in my SQL with the trim function so the Util.transformToHTML is unnecessary (for clarification, here's the method): public static String transformToHTML(Integer number) { String result = ""; try { result = number.toString(); } catch (Exception e) {} return result; } What I'd like to know is a) Can I get the date in the format I want and skip additional processing thus shortening the processing time? b) Is there a better way to do this? We're talking about XML files that are in the 50 MB - 250 MB filesize category.

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• Domain-Driven-Design question

  - by Michael

  Hello everyone, I have a question about DDD. I'm building a application to learn DDD and I have a question about layering. I have an application that works like this: UI layer calls = Application Layer - Domain Layer - Database Here is a small example of how the code looks: //****************UI LAYER************************ //Uses Ioc to get the service from the factory. //This factory would be in the MyApp.Infrastructure.dll IImplementationFactory factory = new ImplementationFactory(); //Interface and implementation for Shopping Cart service would be in MyApp.ApplicationLayer.dll IShoppingCartService service = factory.GetImplementationFactory<IShoppingCartService>(); //This is the UI layer, //Calling into Application Layer //to get the shopping cart for a user. //Interface for IShoppingCart would be in MyApp.ApplicationLayer.dll //and implementation for IShoppingCart would be in MyApp.Model. IShoppingCart shoppingCart = service.GetShoppingCartByUserName(userName); //Show shopping cart information. //For example, items bought, price, taxes..etc ... //Pressed Purchase button, so even for when //button is pressed. //Uses Ioc to get the service from the factory again. IImplementationFactory factory = new ImplementationFactory(); IShoppingCartService service = factory.GetImplementationFactory<IShoppingCartService>(); service.Purchase(shoppingCart); //**********************Application Layer********************** public class ShoppingCartService : IShoppingCartService { public IShoppingCart GetShoppingCartByUserName(string userName) { //Uses Ioc to get the service from the factory. //This factory would be in the MyApp.Infrastructure.dll IImplementationFactory factory = new ImplementationFactory(); //Interface for repository would be in MyApp.Infrastructure.dll //but implementation would by in MyApp.Model.dll IShoppingCartRepository repository = factory.GetImplementationFactory<IShoppingCartRepository>(); IShoppingCart shoppingCart = repository.GetShoppingCartByUserName(username); //Do shopping cart logic like calculating taxes and stuff //I would put these in services but not sure? ... return shoppingCart; } public void Purchase(IShoppingCart shoppingCart) { //Do Purchase logic and calling out to repository ... } } I've seem to put most of my business rules in services rather than the models and I'm not sure if this is correct? Also, i'm not completely sure if I have the laying correct? Do I have the right pieces in the correct place? Also should my models leave my domain model? In general I'm I doing this correct according DDD? Thanks!

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• Object relationships

  - by Hammerstein

  This stems from a recent couple of posts I've made on events and memory management in general. I'm making a new question as I don't think the software I'm using has anything to do with the overall problem and I'm trying to understand a little more about how to properly manage things. This is ASP.NET. I've been trying to understand the needs for Dispose/Finalize over the past few days and believe that I've got to a stage where I'm pretty happy with when I should/shouldn't implement the Dispose/Finalize. 'If I have members that implement IDisposable, put explicit calls to their dispose in my dispose method' seems to be my understanding. So, now I'm thinking maybe my understanding of object lifetimes and what holds on to what is just wrong! Rather than come up with some sample code that I think will illustrate my point, I'm going to describe as best I can actual code and see if someone can talk me through it. So, I have a repository class, in it I have a DataContext that I create when the repository is created. I implement IDisposable, and when my calling object is done, I call Dispose on my repository and explicitly call DataContext.Dispose( ). Now, one of the methods of this class creates and returns a list of objects that's handed back to my front end. Front End - Controller - Repository - Controller - Front End. (Using Redgate Memory Profiler, I take a snapshot of my software when the page is first loaded). My front end creates a controller object on page load and then makes a request to the repository sending back a list of items. When the page is finished loading, I call Dispose on the controller which in turn calls dispose on the context. In my mind, that should mean that my connection is closed and that I have no instances of my controller class. If I then refresh the page, it jumps to two 'Live' instances of the controller class. If I look at the object retention graph, the objects I created in my call to the list are being held onto ultimately by what looks like Linq. The controller/repository aside, if I create a list of objects somewhere, or I create an object and return it somewhere, am I safe to just assume that .NET will eventually come and clean things up for me or is there a best practice? The 'Live' instances suggest to me that these are still in memory and active objects, the fact that RMP apparently forces GC doesn't mean anything?

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• MySQL Hibernate sort on 2 columns

  - by sammichy

  I have a table as follows Table item { ID - Primary Key content - String published_date - When the content was published create_date - When this database entry was created } Every hour (or specified time interval) I run a process to update this table with data from different sources (websites). I want to display the results according to the following rules. 1. The entries created each time the process runs should be grouped together. So the entries from the 2nd process run will always be after the entries from the first process run even if the published_date of an entry from the first run is after the published_date of an entry from the 2nd run. 2. Within the grouping by run, the entries by sorted by published_date 3. Another restriction is that I prefer that data from the same source not be grouped together. If I do the sort by create_date, published_date I will end up with data from source a, data from source b etc. I prefer that the data within each hour be mixed up for better presentation If I add a column to this table and store a counter which increments each time the process is run, it is possible to create a query to sort first by counter and then by published_dt. Is there a way to do it without adding a field? I'm using Hibernate over MySQL. e.g. Hour 1 (run 1) 4 rows collected from site a (rows 1-4) 3 rows collected from site b (rows 5-7) hour 2 (run 2) 2 row collected from site a (rows 8-9) 3 rows collected from site b (rows 10-12) ... After each run, new records are added to the database from each website. The create date is the time when the record was created in the database. The published date is part of the content and is read in from the external source. When the results are displayed I would like rows to be grouped together based on the hour they were published in. So rows 1-7 would be displayed before rows 8-12. Within each hourly grouping, I would like to sort the results by published date (timestamp). This is necessary so that the posts from all the sites collected in that hour are not grouped together but rather mixed in with each other.

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• Move an object in the direction of a bezier curve?

  - by Sent1nel

  I have an object with which I would like to make follow a bezier curve and am a little lost right now as to how to make it do that based on time rather than the points that make up the curve. .::Current System::. Each object in my scene graph is made from position, rotation and scale vectors. These vectors are used to form their corresponding matrices: scale, rotation and translation. Which are then multiplied in that order to form the local transform matrix. A world transform (Usually the identity matrix) is then multiplied against the local matrix transform. class CObject { public: // Local transform functions Matrix4f GetLocalTransform() const; void SetPosition(const Vector3f& pos); void SetRotation(const Vector3f& rot); void SetScale(const Vector3f& scale); // Local transform Matrix4f m_local; Vector3f m_localPostion; Vector3f m_localRotation; // rotation in degrees (xrot, yrot, zrot) Vector3f m_localScale; } Matrix4f CObject::GetLocalTransform() { Matrix4f out(Matrix4f::IDENTITY); Matrix4f scale(), rotation(), translation(); scale.SetScale(m_localScale); rotation.SetRotationDegrees(m_localRotation); translation.SetTranslation(m_localTranslation); out = scale * rotation * translation; } The big question I have are 1) How do I orientate my object to face the tangent of the Bezier curve? 2) How do I move that object along the curve without just setting objects position to that of a point on the bezier cuve? Heres an overview of the function thus far void CNodeControllerPieceWise::AnimateNode(CObject* pSpatial, double deltaTime) { // Get object latest pos. Vector3f posDelta = pSpatial->GetWorldTransform().GetTranslation(); // Get postion on curve Vector3f pos = curve.GetPosition(m_t); // Get tangent of curve Vector3f tangent = curve.GetFirstDerivative(m_t); } Edit: sorry its not very clear. I've been working on this for ages and its making my brain turn to mush. I want the object to be attached to the curve and face the direction of the curve. As for movement, I want to object to follow the curve based on the time this way it creates smooth movement throughout the curve.

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• jquery animation problem using stop

  - by Flanders

  Hi! When running a Jquery animation like slideDown(), it looks like a number of element-specific css properties is set to be updated at a specific interval and when the animation is complete these properties are unset and the display property is simply set to auto or whatever. At least in firebug you can't see those temporary properties any more. The problem I've encountered is the scenario where we stop the slide down with stop(). The element is then left with the current temporary css values. Which is fine because it has to, but let us say that I stoped the slidedown because I have decided to slide it back up again a bit prematurely. It would look something like this: $(this).slideDown(2000) //The below events is not in queue but will rather start execute almost simultaneously as the above line. (dont remember the exact syntax) $(this).delay(1000).stop().slideUp(2000) The above code might not make much sense, but the point is: After 1 second of sliding down the animation is stopped and it starts to slide back up. Works like a charm. BUT!!! And here is the problem. Once it it has slid back up the elements css properties are reset to the exact values it had 1000ms into the slideDown() animation (when stop() was called). If we now try to run the following: $(this).slideDown(2000) It will slide down to the very point the prior slideDown was aborted and not further at half the speed (since it uses the same time for approximately half the height). This is because the css properties were saved as I see it. But it is not especially wished for. Of course I want it to slide all the way down this time. Due to UI interaction that is hard to predict everything might soon break. The longer animations we use increases the risk of something like this happening. Is this to be considered a bug, or am I doing something wrong? Or maybe it's just a feature that is not supported? I guess I can use a callback function to reset the css properties, but depending on the animation used, different css properties are used to render it, and covering your back would result in quite a not-so-fancy solution.

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• Rails controller not rendering correct view when form is force-submitted by Javascript

  - by whazzmaster

  I'm using Rails with jQuery, and I'm working on a page for a simple site that prints each record to a table. The only editable field for each record is a checkbox. My goal is that every time a checkbox is changed, an ajax request updates that boolean attribute for the record (i.e., no submit button). My view code: <td> <% form_remote_tag :url => admin_update_path, :html => { :id => "form#{lead.id}" } do %> <%= hidden_field :lead, :id, :value => lead.id %> <%= check_box :lead, :contacted, :id => "checkbox"+lead.id.to_s, :checked => lead.contacted, :onchange => "$('#form#{lead.id}').submit();" %> <% end %> </td> In my routes.rb, admin_update_path is defined by map.admin_update 'update', :controller => "admin", :action => "update", :method => :post I also have an RJS template to render back an update. The contents of this file is currently just for testing (I just wanted to see if it worked, this will not be the ultimate functionality on a successful save)... page << "$('#checkbox#{@lead.id}').hide();" When clicked, the ajax request is successfully sent, with the correct params, and the action on the controller can retrieve the record and update it just fine. The problem is that it doesn't send back the JS; it changes the page in the browser and renders the generated Javascript as plain text rather than executing it in-place. Rails does some behind-the-scenes stuff to figure out if the incoming request is an ajax call, and I can't figure out why it's interpreting the incoming request as a regular web request as opposed to an ajax request. I may be missing something extremely simple here, but I've kind-of burned myself out looking so I thought I'd ask for another pair of eyes. Thanks in advance for any info!

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• Reason why UIImage gives me a 'distorted' image sometimes

  - by Cedric Vandendriessche

  I have a custom UIView with a UILabel and a UIImageView subview. (tried using UIImageView subclass aswell). I assign an image to it and add the view to the screen. I wrote a function which adds the amount of LetterBoxes to the screen (my custom class): - (void)drawBoxesForWord:(NSString *)word { if(boxesContainer == nil) { /* Create a container for the LetterBoxes (animation purposes) */ boxesContainer = [[UIView alloc] initWithFrame:CGRectMake(0, 205, 320, 50)]; [self.view addSubview:boxesContainer]; } /* Calculate width of letterboxes */ NSInteger numberOfCharacters = [word length]; CGFloat totalWidth = numberOfCharacters * 28 + (numberOfCharacters - 1) * 3; CGFloat leftCap = (320 - totalWidth) / 2; [letters removeAllObjects]; /* Draw the boxes to the screen */ for (int i = 0; i < numberOfCharacters; i++) { LetterBox *letter = [[LetterBox alloc] initWithFrame:CGRectMake(leftCap + i * 31 , 0, 28, 40)]; [letters addObject:letter]; [boxesContainer addSubview:letter]; [letter release]; }} This gives me the image below: http://www.imgdumper.nl/uploads2/4ba3b2c72bb99/4ba3b2c72abfd-Goed.png But sometimes it gives me this: imgdumper.nl/uploads2/4ba3b2d888226/4ba3b2d88728a-Fout.png I add them to the same boxesContainer but they first remove themselves from the superview, so it's not like you see them double or something. What I find weird is that they are all good or all bad.. This is the init function for my LetterBox: if (self == [super initWithFrame:aRect]) { /* Create the box image with same frame */ boxImage = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height)]; boxImage.contentMode = UIViewContentModeScaleAspectFit; boxImage.image = [UIImage imageNamed:@"SpaceOpen.png"]; [self addSubview:boxImage]; /* Create the label with same frame */ letterLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height)]; letterLabel.backgroundColor = [UIColor clearColor]; letterLabel.font = [UIFont fontWithName:@"ArialRoundedMTBold" size:26]; letterLabel.textColor = [UIColor blackColor]; letterLabel.textAlignment = UITextAlignmentCenter; [self addSubview:letterLabel]; } return self;} Does anyone have an idea why this could be? I'd rather have them display correctly every time :)

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