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• Getting started with massive data

  - by Max

  I'm a math guy and occasionally do some statistics/machine learning analysis consulting projects on the side. The data I have access to are usually on the smaller side, at most a couple hundred of megabytes (and almost always far less), but I want to learn more about handling and analyzing data on the gigabyte/terabyte scale. What do I need to know and what are some good resources to learn from? Hadoop/MapReduce is one obvious start. Is there a particular programming language I should pick up? (I primarily work now in Python, Ruby, R, and occasionally Java, but it seems like C and Clojure are often used for large-scale data analysis?) I'm not really familiar with the whole NoSQL movement, except that it's associated with big data. What's a good place to learn about it, and is there a particular implementation (Cassandra, CouchDB, etc.) I should get familiar with? Where can I learn about applying machine learning algorithms to huge amounts of data? My math background is mostly on the theory side, definitely not on the numerical or approximation side, and I'm guessing most of the standard ML algorithms don't really scale. Any other suggestions on things to learn would be great!

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• Is this OleDbDataAdapter bug

  - by ????

  It doesn't look to me OleDbDataAdapter should throw an exception on trying to fill DataSet for a db table column of type decimal(28,3). The message is "The numerical value is too large to fit into a 96 bit decimal". Could you just check this, I have no significant experience with ADO.NET and OLE DB components? The VB.NET code we have in the application is this: Dim dbDataSet As New DataSet Dim dbDataAdapter As OleDbDataAdapter Dim dbCommand As OleDbCommand Dim conn As OleDbConnection Dim connectionString As String 'parts where connectionString is set conn = New OleDbConnection(connectionString) 'part where sqlQuery is set but it ends up being "SELECT Price As 'Price' From PricebookView" - Price is of type decimal(28,3) dbCommand = New OleDbCommand(sqlQuery, conn) dbCommand.CommandTimeout = cmdTimeout dbDataAdapter = New OleDbDataAdapter(dbCommand) dbDataAdapter.Fill(dbDataSet) The last line is where the exception is thrown and the top of the stack trace is: at System.Data.ProviderBase.DbBuffer.ReadNumeric(Int32 offset) at System.Data.OleDb.ColumnBinding.Value_NUMERIC() at System.Data.OleDb.ColumnBinding.Value() at System.Data.OleDb.OleDbDataReader.GetValues(Object[] values) at System.Data.ProviderBase.DataReaderContainer.CommonLanguageSubsetDataReader.GetValues(Object[] values) at System.Data.ProviderBase.SchemaMapping.LoadDataRow() at System.Data.Common.DataAdapter.FillLoadDataRow(SchemaMapping mapping) at System.Data.Common.DataAdapter.FillFromReader(DataSet dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) at System.Data.Common.DataAdapter.Fill(DataSet dataSet, String srcTable, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet) ... I am not sure why does it try to set the value to Int32. Thank you for the time !

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• MKL Accelerated Math Libraries for Java...

  - by Kaopua

  I've looked at the related threads on StackOverflow and Googled with not much luck. I'm also very new to Java (I'm coming from a C# and .NET background) so please bear with me. There is so much available in the Java world it's pretty overwhelming. I'm starting on a new Java-on-Linux project that requires some heavy and highly repetitious numerical calculations (i.e. statistics, FFT, Linear Algebra, Matrices, etc.). So maximizing the performance of the mathematical operations is a requirement, as is ensuring the math is correct. So hence I have an interest in finding a Java library that perhaps leverages native acceleration such as MKL, and is proven (so commercial options are definitely a possibility here). In the .NET space there are highly optimized and MKL accelerated commercial Mathematical libraries such as Centerspace NMath and Extreme Optimization. Is there anything comparable in Java? Most of the math libraries I have found for Java either do not seem to be actively maintained (such as Colt) or do not appear to leverage MKL or other native acceleration (such as Apache Commons Math). I have considered trying to leverage MKL directly from Java myself (e.g. JNI), but me being new to Java (let alone interoperating between Java and native libraries) it seemed smarter finding a Java library that has already done this correctly, efficiently, and is proven. Again I apologize if I am mistaken or misguided (even in regarding any libraries I've mentioned) and my ignorance of the Java offerings. It's a whole new world for me coming from the heavily commercialized Microsoft stock so I could easily be mistaken on where to look and regarding the Java libraries I've mentioned. I would greatly appreciate any help or advice.

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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• How to get the actual address of a pointer in C?

  - by Airjoe

  BACKGROUND: I'm writing a single level cache simulator in C for a homework assignment, and I've been given code that I must work from. In our discussions of the cache, we were told that the way a small cache can hold large addresses is by splitting the large address into the position in the cache and an identifying tag. That is, if you had an 8 slot cache but wanted to store something with address larger than 8, you take the 3 (because 2^3=8) rightmost bits and put the data in that position; so if you had address 22 for example, binary 10110, you would take those 3 rightmost bits 110, which is decimal 5, and put it in slot 5 of the cache. You would also store in this position the tag, which is the remaining bits 10. One function, cache_load, takes a single argument, and integer pointer. So effectively, I'm being given this int* addr which is an actual address and points to some value. In order to store this value in the cache, I need to split the addr. However, the compiler doesn't like when I try to work with the pointer directly. So, for example, I try to get the position by doing: npos=addr%num_slots The compiler gets angry and gives me errors. I tried casting to an int, but this actually got me the value that the pointer was pointing to, not the numerical address itself. Any help is appreciated, thanks!

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• PHP returns invalid MySQL resource

  - by DeadMG

  $LDATE = '#' . $_REQUEST['LDateDay'] . '/' . $_REQUEST['LDateMonth'] . '/' . $_REQUEST['LDateYear'] . '#'; $RDATE = '#' . $_REQUEST['RDateDay'] . '/' . $_REQUEST['RDateMonth'] . '/' . $_REQUEST['RDateYear'] . '#'; include("../../sql.php"); $myconn2 = mysql_connect(/*removed*/, $username, $password); mysql_select_db(/*removed*/, $myconn2); $LSQLRequest = "SELECT * FROM flight WHERE DepartureDate = ".$LDATE; $LFlights = mysql_query($LSQLRequest, $myconn2); $RSQLRequest = "SELECT * FROM flight WHERE DepartureDate = ".$RDATE; $RFlights = mysql_query($RSQLRequest, $myconn2); Assuming that all the $_REQUESTs are valid numerical values for their appropriate fields in the day/month/year field, how can LFlights and RFlights be invalid? When I polled the whole database I got hundreds of results so I know that the database and connection data is fine, and the field DepartureDate exists too.

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• Drupal WebForm with CCK content types. For anonymous users.

  - by thepearson

  I am probably asking a noob question... however: I have a Drupal site that the customer has a web form where anonymous users can fill in to order some posters (there is 3 to choose from). These are free and at the moment they user just states in the body of a textarea what posters they want. The site owner wants to now add more posters and now wants the ability to have each poster listed in the web form with a field for quantity next to them. When the web for is submitted it will post the node title and quantity to the web form along with the required information. I have researched using UC but it's too much of a eCom solution for such a simple requirement. I also looked at SimpleCart, Flag and Session favorites, all of which aren't really what I need. So I am looking for a simple way to itterate over all the "Poster" content types, and display them on the webform page with a quantity numerical field to be submitted with the web form for each poster. Currently I have: CCK Poster Title Image WebForm OrderPoster Name Email Address Details What I am looking for is a page that does the following: WebForm OrderPosters: Poster 1 [form qty text input for poster 1] Poster 2 [form qty text input for poster 2] Poster 3 [form qty text input for poster 3] ... Poster n [form qty text input for posters n] Name Email Address Details I'd imagine there is a simple way to do this, but I can't seem to find articles of customizing "WebForm" forms. Any help would be much appreciated.

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• RichFaces a4j:support parameter passing

  - by Mark Lewis

  Hello I have a number of rich:inplaceInput tags in RichFaces which represent numbers in an array. The validator allows integers only. When a user clicks in an input and changes a value, how can I get the bean to sort the array given the new number and reRender the list of rich:inplaceInput tags so that they're in numerical order? EG <a4j:region> <rich:dataTable value="#{MyBacking.config}" var="feed" cellpadding="0" cellspacing="0" width="100%" border="0" columns="5" id="Admin"> ... <a4j:repeat... <a4j:region id="MsgCon"> <rich:inplaceInput value="#{h.id}" validator="#{MyBacking.validateID}" id="andID" showControls="true"> <a4j:support event="onviewactivated" action="#{MyBacking.sort}" reRender="Admin" /> </rich:inplaceInput> </a4j:region> </a4j:repeat> </data:Table> </a4j:region> Note I do NOT want to use dataTable sort functions. The table is complicated and I've specified id="Admin" (ie the whole table) to reRender as I've not found a way to send more localised values to the backing bean through the inplaceInput. This question is about how to use a4j:support action attribute to call the sort method so that when the reRender rerenders the component, it outputs the list in sorted order. I have the sort method working ok when I click a button to sort, but I want to have the list sorted automatically as soon as a new valid value is entered into the inplaceInput component. Thanks

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• Easiest way to plot values as symbols in scatter plot?

  - by AllenH

  In an answer to an earlier question of mine regarding fixing the colorspace for scatter images of 4D data, Tom10 suggested plotting values as symbols in order to double-check my data. An excellent idea. I've run some similar demos in the past, but I can't for the life of me find the demo I remember being quite simple. So, what's the easiest way to plot numerical values as the symbol in a scatter plot instead of 'o' for example? Tom10 suggested plt.txt(x,y,value)- and that is the implementation used in a number of examples. I however wonder if there's an easy way to evaluate "value" from my array of numbers? Can one simply say: str(valuearray) ? Do you need a loop to evaluate the values for plotting as suggested in the matplotlib demo section for 3D text scatter plots? Their example produces: However, they're doing something fairly complex in evaluating the locations as well as changing text direction based on data. So, is there a cute way to plot x,y,C data (where C is a value often taken as the color in the plot data- but instead I wish to make the symbol)? Again, I think we have a fair answer to this- I just wonder if there's an easier way?

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• Overlapping template partial specialization when wanting an "override" case: how to avoid the error?

  - by user173342

  I'm dealing with a pretty simple template struct that has an enum value set by whether its 2 template parameters are the same type or not. template<typename T, typename U> struct is_same { enum { value = 0 }; }; template<typename T> struct is_same<T, T> { enum { value = 1 }; }; This is part of a library (Eigen), so I can't alter this design without breaking it. When value == 0, a static assert aborts compilation. So I have a special numerical templated class SpecialCase that can do ops with different specializations of itself. So I set up an override like this: template<typename T> struct SpecialCase { ... }; template<typename LT, typename RT> struct is_same<SpecialCase<LT>, SpecialCase<RT>> { enum { value = 1 }; }; However, this throws the error: more than one partial specialization matches the template argument list Now, I understand why. It's the case where LT == RT, which steps on the toes of is_same<T, T>. What I don't know is how to keep my SpecialCase override and get rid of the error. Is there a trick to get around this? edit: To clarify, I need all cases where LT != RT to also be considered the same (have value 1). Not just LT == RT.

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• barebones sort algorithm

  - by user309322

  i have been asked to make a simple sort aglorithm to sort a random series of 6 numbers into numerical order. However i have been asked to do this using "Barebones" a theoretical language put forward in the Book Computer Science an overview. Some information on the language can be found here http://www.brouhaha.com/~eric/software/barebones/ Just to clarify i am a student teacher and have been doing anaysis on "mini-programing languages" and their uses in a teaching environment, i suggested to my tutor that i look at barebones and asked what sort of exmaple program i should write . He suggested a simple sort algorithm. Now since looking at the language i cant understand how i can do this without using arrays and if statements. The code to swap the value of variables would be while a not 0 do; incr Aux1; decr a; end; while b not 0 do; incr Aux2 decr b end; while Aux1 not 0 do; incr a; decr Aux1; end; while Aux2 not 0 do; incr b; decr Aux2; end; however the language does not provide < or operators

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• How does mercurial's bisect work when the range includes branching?

  - by Joshua Goldberg

  If the bisect range includes multiple branches, how does hg bisect's search work. Does it effectively bisect each sub-branch (I would think that would be inefficient)? For instance, borrowing, with gratitude, a diagram from an answer to this related question, what if the bisect got to changeset 7 on the "good" right-side branch first. @ 12:8ae1fff407c8:bad6 | o 11:27edd4ba0a78:bad5 | o 10:312ba3d6eb29:bad4 |\ | o 9:68ae20ea0c02:good33 | | | o 8:916e977fa594:good32 | | | o 7:b9d00094223f:good31 | | o | 6:a7cab1800465:bad3 | | o | 5:a84e45045a29:bad2 | | o | 4:d0a381a67072:bad1 | | o | 3:54349a6276cc:good4 |/ o 2:4588e394e325:good3 | o 1:de79725cb39a:good2 | o 0:2641cc78ce7a:good1 Will it then look only between 7 and 12, missing the real first-bad that we care about? (thus using "dumb" numerical order) or is it smart enough to use the full topography and to know that the first bad could be below 7 on the right-side branch, or could still be anywhere on the left-side branch. The purpose of my question is both (a) just to understand the algorithm better, and (b) to understand whether I can liberally extend my initial bisect range without thinking hard about what branch I go to. I've been in high-branching bisect situations where it kept asking me after every test to extend beyond the next merge, so that the whole procedure was essentially O(n). I'm wondering if I can just throw the first "good" marker way back past some nest of merges without thinking about it much, and whether that would save time and give correct results.

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• Thread-safety of read-only memory access

  - by Edmund

  I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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• How to perform Rails model validation checks within model but outside of filters using ledermann-rails-settings and extensions

  - by user1277160

  Background I'm using ledermann-rails-settings (https://github.com/ledermann/rails-settings) on a Rails 2/3 project to extend virtually the model with certain attributes that don't necessarily need to be placed into the DB in a wide table and it's working out swimmingly for our needs. An additional reason I chose this Gem is because of the post How to create a form for the rails-settings plugin which ties ledermann-rails-settings more closely to the model for the purpose of clean form_for usage for administrator GUI support. It's a perfect solution for addressing form_for support although... Something that I'm running into now though is properly validating the dynamic getters/setters before being passed to the ledermann-rails-settings module. At the moment they are saved immediately, regardless if the model validation has actually fired - I can see through script/console that validation errors are being raised. Example For instance I would like to validate that the attribute :foo is within the range of 0..100 for decimal usage (or even a regex). I've found that with the previous post that I can use standard Rails validators (surprise, surprise) but I want to halt on actually saving any values until those are addressed - ensure that the user of the GUI has given 61.43 as a numerical value. The following code has been borrowed from the quoted post. class User < ActiveRecord::Base has_settings validates_inclusion_of :foo, :in => 0..100 def self.settings_attr_accessor(*args) >>SOME SORT OF UNLESS MODEL.VALID? CHECK HERE args.each do |method_name| eval " def #{method_name} self.settings.send(:#{method_name}) end def #{method_name}=(value) self.settings.send(:#{method_name}=, value) end " end >>END UNLESS end settings_attr_accessor :foo end Anyone have any thoughts here on pulling the state of the model at this point outside of having to put this into a before filter? The goal here is to be able to use the standard validations and avoid rolling custom validation checks for each new settings_attr_accessor that is added. Thanks!

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• Defining default value in combobox in CakePHP

  - by Keyur

  <?php echo $form->create('admin_merchant_form', array('action' => '#')); echo $form->input('company_name', array('label' => 'Company Name')); echo $form->input('ac_owner', array('label' => 'Account Owner', 'options' => array('a','b','b'), 'default' => $merchant_select)); echo $form->end('Update'); ?> This is CakePHP code to generate a form with one combobox containing the values "a,b,c" and assigning the default value as $merchant_select which is numerical data. Now the problem is when I assign like 'default'=1 it returns 'b' in the combobox as default value but when writing 'default' = $merchant_select the combobox shows only the first value which is 'a'. The $merchant_select variable is assigned a numeric value equal to merchant's id which 1,2 or 3 when I select any row in the grid. And I also have JavaScript code which alerts with the merchant value when I select any row in the grid so the numeric data is definitely assigned to the $merchant_select variable.

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• Partitioning data set in r based on multiple classes of observations

  - by Danny

  I'm trying to partition a data set that I have in R, 2/3 for training and 1/3 for testing. I have one classification variable, and seven numerical variables. Each observation is classified as either A, B, C, or D. For simplicity's sake, let's say that the classification variable, cl, is A for the first 100 observations, B for observations 101 to 200, C till 300, and D till 400. I'm trying to get a partition that has 2/3 of the observations for each of A, B, C, and D (as opposed to simply getting 2/3 of the observations for the entire data set since it will likely not have equal amounts of each classification). When I try to sample from a subset of the data, such as sample(subset(data, cl=='A')), the columns are reordered instead of the rows. To summarize, my goal is to have 67 random observations from each of A, B, C, and D as my training data, and store the remaining 33 observations for each of A, B, C, and D as testing data. I have found a very similar question to mine, but it did not factor in multiple variables. I feel silly asking this question because it seems so simple, but I'm stumped. Also, this is my first question on this site, so I apologize in advance for any faux pas on my part.

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• Building static (but complicated) lookup table using templates.

  - by MarkD

  I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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• Simplest way to mix sequences of types with iostreams?

  - by Kylotan

  I have a function void write<typename T>(const T&) which is implemented in terms of writing the T object to an ostream, and a matching function T read<typename T>() that reads a T from an istream. I am basically using iostreams as a plain text serialisation format, which obviously works fine for most built-in types, although I'm not sure how to effectively handle std::strings just yet. I'd like to be able to write out a sequence of objects too, eg void write<typename T>(const std::vector<T>&) or an iterator based equivalent (although in practice, it would always be used with a vector). However, while writing an overload that iterates over the elements and writes them out is easy enough to do, this doesn't add enough information to allow the matching read operation to know how each element is delimited, which is essentially the same problem that I have with a single std::string. Is there a single approach that can work for all basic types and std::string? Or perhaps I can get away with 2 overloads, one for numerical types, and one for strings? (Either using different delimiters or the string using a delimiter escaping mechanism, perhaps.)

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• How to generate a monotone MART ROC in R?

  - by user1521587

  I am using R and applying MART (Alg. for multiple additive regression trees) on a training set to build prediction models. When I look at the ROC curve, it is not monotone. I would be grateful if someone can help me with how I should fix this. I am guessing the issue is that initially, MART generates n trees and if these trees are not the same for all the models I am building, the results will not be comparable. Here are the steps I take: 1) Fix the false-negative cost, c_fn. Let cost = c(0, 1, c_fn, 0). 2) use the following line to build the mart model: mart(x, y, lx, martmode='class', niter=2000, cost.mtx=cost) where x is the matrix of training set variables, y is the observation matrix, lx is the matrix which specifies which of the variables in x is numerical, which one categorical. 3) I predict the test set observations using the mart model found in step 2 using this line: y_pred = martpred(x_test, probs=T) 4) I compute the false-positive and false-negative errors as follows: t = 1/(1+c_fn) %threshold based on Bayes optimal rule where c_fp=1 and c_fn. p_0 = length(which(y_test==1))/dim(y_test)[1] p_01 = sum(1*(y_pred[,2]t & y_test==0))/dim(y_test)[1] p_11 = sum(1*(y_pred[,2]t & y_test==1))/dim(y_test)[1] p_fp = p_01/(1-p_0) p_tp = p_11/p_0 5) repeat step 1-4 for a new false-negative cost.

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• Many users, many cpus, no delays. Good for cloud?

  - by Eric

  I wish to set up a CPU-intensive time-important query service for users on the internet. A usage scenario is described below. Is cloud computing the right way to go for such an implementation? If so, what cloud vendor(s) cater to this type of application? I ask specifically, in terms of: 1) pricing 2) latency resulting from: - slow CPUs, instance creations, JIT compiles, etc.. - internal management and communication of processes inside the cloud (e.g. a queuing process and a calculation process) - communication between cloud and end user 3) ease of deployment A usage scenario I am expecting is: - A typical user sends a query (XML of size around 1K) once every 30 seconds on average. - Each query requires a numerical computation of average time 0.2 sec and max time 1 sec on a 1 GHz Pentium. The computation requires no data other than the query itself and is performed by the same piece of code each time. - The delay a user experiences between sending a query and receiving a response should be on average no more than 2 seconds and in general no more than 5 seconds. - A background save to a DB of the response should occur (not time critical) - There can be up to 30000 simultaneous users - i.e., on average 1000 queries a second, each requiring an average 0.2 sec calculation, so that would necessitate around 200 CPUs. Currently I'm look at GAE Java (for quicker deployment and less IT hassle) and EC2 (Speed and price optimization) as options. Where can I learn more about the right way to set ups such a system? past threads, different blogs, books, etc.. BTW, if my terminology is wrong or confusing, please let me know. I'd greatly appreciate any help.

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• Finding and marking the largest of three values in a two dimensional array

  - by DavidYell

  I am working on a display screen for our office, and I can't seem to think of a good way to find the largest numerical value in a set of data in a two dimensional array. I've looked at using max() and also asort() but they don't seem to cope with a two dimensional array. I'm returning my data through our mysql class, so the rows are returned in a two dimensional array. Array( [0] => Array( [am] => 12, [sales] => 981), [1] => Array( [am] => 43, [sales] => 1012), [2] => Array( [am] => 17, [sales] => 876) ) I need to output a class when foreaching the data in my table for the AM with the highest sales value. Short of comparing them all in if statements. I have tried to get max() on the array, but it returns an array, as it's look within the dimension. When pointing it at a specific dimension it returns the key not the value. I figured that I could asort() the array and pop the top value off, store it in a variable and then compare against that in my foreach() loop, but that seems to have trouble sorting across two dimensions. Lastly, I figured that I could foreach() the values, comparing them against the previous one each time, untill I found the largest. This approach however means storing every value, luckily only three, but then comparing against them all again. Surely there must be a simpler way to achieve this, short of converting it into a single dimension array, then doing an asort() on that?

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• finding the maximum in series

  - by peril brain

  I need to know a code that will automatically:- search a specific word in excel notes it row or column number (depends on data arrangement) searches numerical type values in the respective row or column with that numeric value(suppose a[7][0]or a[0][7]) it compares all other values of respective row or column(ie. a[i][0] or a[0][i]) sets that value to the highest value only if IT HAS GOT NO FORMULA FOR DERIVATION i know most of coding but at a few places i got myself stuck... i'm writing a part of my program upto which i know: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; using Microsoft.Office.Interop; using Excel = Microsoft.Office.Interop.Excel; Excel.Application oExcelApp; namespace a{ class b{ static void main(){ try { oExcelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application"); ; if(oExcelApp.ActiveWorkbook != null) {Excel.Workbook xlwkbook = (Excel.Workbook)oExcelApp.ActiveWorkbook; Excel.Worksheet ws = (Excel.Worksheet)xlwkbook.ActiveSheet; Excel.Range rn; rn = ws.Cells.Find("maximum", Type.Missing, Excel.XlFindLookIn.xlValues, Excel.XlLookAt.xlPart,Excel.XlSearchOrder.xlByRows, Excel.XlSearchDirection.xlNext, false, Type.Missing, Type.Missing); }}} now ahead of this i only know tat i have to use cell.value2 ,cell.hasformula methods..... & no more idea can any one help me with this..

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• How can I write simulations in Erlang?

  - by rick

  Hi guys, I want to do some numerical stuff in Erlang like this: You've got an array with the following values: [2,3,4] In each iteration, you calculate 0.1 * [n-1] + 0.7 *[n] + 0.2 * [n+1] This becomes the new [n]. If n == 0 then [n-1] = 0. If [n] == length of array then [n] = 0. So I try an example: [2,3,4] calculations: 0.1 * 0 + 0.7 * 2 + 0.2 * 3 = 2 0.1 * 2 + 0.7 * 3 + 0.2 * 4 = 3.1 0.1 * 3 + 0.7 * 4 + 0.2 * 0 = 3.1 So [2,3,4] becomes to [2, 3.1, 3.1] after one iteration. I know how to write this in a non-functional language like C. But I have difficulties to imagine, how this could be done in Erlang. I found some tutorials on how you read a file to a list. So this is not the problem. How can I spawn different Erlang processes that each process has one element of the list? How can I do calculations by communicating with 'the neighbors', so that the neighbors know where their neigbors are generically, without specifying each? How can I collect the data into a list? Eventually, is it possible to solve that problem in Erlang at all? Thanks for your help.

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• finding the maximum in the range

  - by comfreak

  I need to know a code that will automatically:- search a specific word in excel notes it row or column number (depends on data arrangement) searches numerical type values in the respective row or column with that numeric value(suppose a[7][0]or a[0][7]) it compares all other values of respective row or column(ie. a[i][0] or a[0][i]) sets that value to the highest value only if IT HAS GOT NO FORMULA FOR DERIVATION i know most of coding but at a few places i got myself stuck... i'm writing a part of my program upto which i know: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; using Microsoft.Office.Interop; using Excel = Microsoft.Office.Interop.Excel; Excel.Application oExcelApp; namespace a{ class b{ static void main(){ try { oExcelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application"); ; if(oExcelApp.ActiveWorkbook != null) {Excel.Workbook xlwkbook = (Excel.Workbook)oExcelApp.ActiveWorkbook; Excel.Worksheet ws = (Excel.Worksheet)xlwkbook.ActiveSheet; Excel.Range rn; rn = ws.Cells.Find("maximum", Type.Missing, Excel.XlFindLookIn.xlValues, Excel.XlLookAt.xlPart,Excel.XlSearchOrder.xlByRows, Excel.XlSearchDirection.xlNext, false, Type.Missing, Type.Missing); }}} now ahead of this i only know tat i have to use cell.value2 ,cell.hasformula methods..... & no more idea can any one help me with this..

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• search for the maximum

  - by peril brain

  I need to know a code that will automatically:- search a specific word in excel notes it row or column number (depends on data arrangement) searches numerical type values in the respective row or column with that numeric value(suppose a[7][0]or a[0][7]) it compares all other values of respective row or column(ie. a[i][0] or a[0][i]) sets that value to the highest value only if IT HAS GOT NO FORMULA FOR DERIVATION i know most of coding but at a few places i got myself stuck... i'm writing a part of my program upto which i know: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; using Microsoft.Office.Interop; using Excel = Microsoft.Office.Interop.Excel; Excel.Application oExcelApp; namespace a{ class b{ static void main(){ try { oExcelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application"); ; if(oExcelApp.ActiveWorkbook != null) {Excel.Workbook xlwkbook = (Excel.Workbook)oExcelApp.ActiveWorkbook; Excel.Worksheet ws = (Excel.Worksheet)xlwkbook.ActiveSheet; Excel.Range rn; rn = ws.Cells.Find("maximum", Type.Missing, Excel.XlFindLookIn.xlValues, Excel.XlLookAt.xlPart,Excel.XlSearchOrder.xlByRows, Excel.XlSearchDirection.xlNext, false, Type.Missing, Type.Missing); }}} now ahead of this i only know tat i have to use cell.value2 ,cell.hasformula methods..... & no more idea can any one help me with this..

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