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• Finding What You Need in R: function arguments/parameters from outside the function's package

  - by doug

  Often in R, there are a dozen functions scattered across as many packages--all of which have the same purpose but of course differ in accuracy, performance, theoretical rigor, and so on. How do you gather all of these in one place before you start your task? So for instance: the generic plot function. Setting secondary ticks is much easier (IMHO) using a function outside of the base package, minor.tick(nx=n, ny=n, tick.ratio=n), found in Hmisc. Of course, that doesn't show up in plot's docstring. Likewise, the data-input arguments to 'plot' can be supplied by an object returned from the function 'hexbin', again, from a library outside of the base installation (where 'plot' resides). What would be great obviously is a programmatic way to gather these function arguments from the various libraries and put them in a single namespace. edit: (trying to re-state my example just above more clearly:) the arguments to plot supplied in the base package for, e.g., setting the axis tick frequency are xaxp/yaxp; however, one can also set a/t/f via a function outside of the base package, again, as in the minor.tick function from the Hmisc package--but you wouldn't know that just from looking at the plot method signature. Is there a meta function in R for this? So far, as i come across them, i've been manually gathering them in a TextMate 'snippet' (along with the attendant library imports). This isn't that difficult or time consuming, but i can only update my snippet as i find out about these additional arguments/parameters. Is there a canonical R way to do this, or at least an easier way? Just in case that wasn't clear, i am not talking about the case where multiple packages provide functions directed to the same statistic or view (e.g., 'boxplot' in the base package; 'boxplot.matrix' in gplots; and 'bplots' in Rlab). What i am talking is the case in which the function name is the same across two or more packages.

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• Out-of-memory algorithms for addressing large arrays

  - by reve_etrange

  I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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• Solving quadratic programming using R

  - by user702846

  I would like to solve the following quadratic programming equation using ipop function from kernlab : min 0.5*x'*H*x + f'*x subject to: A*x <= b Aeq*x = beq LB <= x <= UB where in our example H 3x3 matrix, f is 3x1, A is 2x3, b is 2x1, LB and UB are both 3x1. edit 1 My R code is : library(kernlab) H <- rbind(c(1,0,0),c(0,1,0),c(0,0,1)) f = rbind(0,0,0) A = rbind(c(1,1,1), c(-1,-1,-1)) b = rbind(4.26, -1.73) LB = rbind(0,0,0) UB = rbind(100,100,100) > ipop(f,H,A,b,LB,UB,0) Error in crossprod(r, q) : non-conformable arguments I know from matlab that is something like this : H = eye(3); f = [0,0,0]; nsamples=3; eps = (sqrt(nsamples)-1)/sqrt(nsamples); A=ones(1,nsamples); A(2,:)=-ones(1,nsamples); b=[nsamples*(eps+1); nsamples*(eps-1)]; Aeq = []; beq = []; LB = zeros(nsamples,1); UB = ones(nsamples,1).*1000; [beta,FVAL,EXITFLAG] = quadprog(H,f,A,b,Aeq,beq,LB,UB); and the answer is a vector of 3x1 equals to [0.57,0.57,0.57]; However when I try it on R, using ipop function from kernlab library ipop(f,H,A,b,LB,UB,0)) and I am facing Error in crossprod(r, q) : non-conformable arguments I appreciate any comment

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• My kernel only works in block (0,0)

  - by ZeroDivide

  I am trying to write a simple matrixMultiplication application that multiplies two square matrices using CUDA. I am having a problem where my kernel is only computing correctly in block (0,0) of the grid. This is my invocation code: dim3 dimBlock(4,4,1); dim3 dimGrid(4,4,1); //Launch the kernel; MatrixMulKernel<<<dimGrid,dimBlock>>>(Md,Nd,Pd,Width); This is my Kernel function __global__ void MatrixMulKernel(int* Md, int* Nd, int* Pd, int Width) { const int tx = threadIdx.x; const int ty = threadIdx.y; const int bx = blockIdx.x; const int by = blockIdx.y; const int row = (by * blockDim.y + ty); const int col = (bx * blockDim.x + tx); //Pvalue stores the Pd element that is computed by the thread int Pvalue = 0; for (int k = 0; k < Width; k++) { Pvalue += Md[row * Width + k] * Nd[k * Width + col]; } __syncthreads(); //Write the matrix to device memory each thread writes one element Pd[row * Width + col] = Pvalue; } I think the problem may have something to do with memory but I'm a bit lost. What should I do to make this code work across several blocks?

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• Ruby CSV in Array

  - by mattrock

  I read a CSV file. This file looks like this 1.00 cm; 2.00cm ; 3.00 cm; ... ; 100 cm 2.00 cm; 4.00 cm; 6.00 cm; ... ; 100 cm 4.00 cm; 8.00 cm; 12.00 cm; ... ; 100cm 8.00 cm; 16.00 cm; 24.00 cm; ... ; 100cm I have already written the following code CSV.foreach("/Users/testUser/Entwicklung/coverrechner/CoverPaperDE.csv", col_sep: ';') do |row| puts row[0] end This produces the following output: 1.00 cm 2.00 cm 4.00 cm 8.00 cm Example: My matrix is constructed 1.1 1.2 1.3 1.4 2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4 4.1 4.2 4.3 4.4 I want the following output 1.1 2.1 3.1 4.1 1.2 2.2 3.2 4.2 ... 4.4 How does it work?

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• MATLAB: svds() not converging

  - by Paul

  So using MATLAB's svds() function on some input data as such: [U, S, V, flag] = svds(data, nSVDs, 'L') I noticed that from run to run with the same data, I'd get drastically different output SVD sizes from run to run. When I checked whether 'flag' was set, I found that it was, indicating that the SVDs had not converged. My normal system here would be that if it really needs to converge, I'd do something like this: flag = 1 svdOpts = struct('tol', 1e-10, 'maxit', 600, 'disp', 0); while flag: if svdOpts.maxit > 1e6 error('There''s a real problem here.') end [U, S, V, flag] = svds(data, nSVDs, 'L', svdOpts) svdOpts.maxit = svdOpts.maxit*2 end But from what I can tell, when you use 'L' as the third argument, the fourth argument is ignored, meaning I just have to deal with the fact that it's not converging? I'm not even really sure how to use the 'sigma' argument in place of the 'L' argument. I've also tried reducing the number of SVDs calculated to no avail. Any help on this matter would be much appreciated. EDIT While following up on the comments below, I found that the problem had to do with the way I was building my data matrices. Turned out I had accidentally inverted a matrix and had an input of size (4000x1) rather than (20x200), which was what was refusing to converge. I also did some more timing tets and found that the fourth argument was not, in fact, being ignored, so that's on me. Thanks for the help guys.

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• rbind.zoo doesn't seem create consistent zoo object

  - by a-or-b

  I want to rbind.zoo two zoo object together. When I was testing I came across the following issue(?)... Note: The below is an example, there is clearly no point to it apart from being illustrative. I have an zoo object, call it, 'X'. I want to break it into two parts and then rbind.zoo them together. When I compare it to the original object then all.equal gives differences. It appears that the '$class' attribute differs, but I can't see how or why. Is I make these xts objects then the all.equal works as expected. i.e. ..... X.date <- as.POSIXct(paste("2003-", rep(1:4, 4:1), "-", sample(1:28, 10, replace = TRUE), sep = "")) X <- zoo(matrix(rnorm(24), ncol = 2), X.date) a <- X[c(1:3), ] # first 3 elements b <- X[c(4:6), ] # second 3 elements c <- rbind.zoo(a, b) # rbind into an object of 6 elements d <- X[c(1:6), ] # all 6 elements all.equal(c, d) # are they equal? ~~~~ all.equal gives me the following difference: "Attributes: < Component 3: Attributes: < Length mismatch: comparison on first 1 components "

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• Triangulation & Direct linear transform

  - by srand

  Following Hartley/Zisserman's Multiview Geometery, Algorithm 12: The optimal triangulation method (p318), I got the corresponding image points xhat1 and xhat2 (step 10). In step 11, one needs to compute the 3D point Xhat. One such method is Direct Linear Transform (DLT), mentioned in 12.2 (p312) and 4.1 (p88). The homogenous method (DLT), p312-313, states that it finds a solution as the unit singular vector corresponding to the smallest singular value of A, thus, A = [xhat1(1) * P1(3,:)' - P1(1,:)' ; xhat1(2) * P1(3,:)' - P1(2,:)' ; xhat2(1) * P2(3,:)' - P2(1,:)' ; xhat2(2) * P2(3,:)' - P2(2,:)' ]; [Ua Ea Va] = svd(A); Xhat = Va(:,end); plot3(Xhat(1),Xhat(2),Xhat(3), 'r.'); However, A is a 16x1 matrix, resulting in a Va that is 1x1. What am I doing wrong (and a fix) in getting the 3D point? For what its worth sample data: xhat1 = 1.0e+009 * 4.9973 -0.2024 0.0027 xhat2 = 1.0e+011 * 2.0729 2.6624 0.0098 P1 = 699.6674 0 392.1170 0 0 701.6136 304.0275 0 0 0 1.0000 0 P2 = 1.0e+003 * -0.7845 0.0508 -0.1592 1.8619 -0.1379 0.7338 0.1649 0.6825 -0.0006 0.0001 0.0008 0.0010 A = <- my computation 1.0e+011 * -0.0000 0 0.0500 0 0 -0.0000 -0.0020 0 -1.3369 0.2563 1.5634 2.0729 -1.7170 0.3292 2.0079 2.6624

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• Reordering Variadic Parameters

  - by void-pointer

  I have come across the need to reorder a variadic list of parameters that is supplied to the constructor of a struct. After being reordered based on their types, the parameters will be stored as a tuple. My question is how this can be done so that a modern C++ compiler (e.g. g++-4.7) will not generate unnecessary load or store instructions. That is, when the constructor is invoked with a list of parameters of variable size, it efficiently pushes each parameter into place based on an ordering over the parameters' types. Here is a concrete example. Assume that the base type of every parameter (without references, rvalue references, pointers, or qualifiers) is either char, int, or float. How can I make it so that all the parameters of base type char appear first, followed by all of those of base type int (which leaves the parameters of base type float last). The relative order in which the parameters were given should not be violated within sublists of homogeneous base type. Example: foo::foo() is called with arguments float a, char&& b, const float& c, int&& d, char e. The tuple tupe is std::tuple<char, char, int, float, float>, and it is constructed like so: tuple_type{std::move(b), e, std::move(d), a, c}. Consider the struct defined below, and assume that the metafunction deduce_reordered_tuple_type is already implemented. How would you write the constructor so that it works as intended? If you think that the code for deduce_reodered_tuple_type, would be useful to you, I can provide it; it's a little long. template <class... Args> struct foo { // Assume that the metafunction deduce_reordered_tuple_type is defined. typedef typename deduce_reordered_tuple_type<Args...>::type tuple_type; tuple_type t_; foo(Args&&... args) : t_{reorder_and_forward_parameters<Args>(args)...} {} }; Edit 1 The technique I describe above does have applications in mathematical frameworks that make heavy use of expression templates, variadic templates, and metaprogramming in order to perform aggressive inlining. Suppose that you wish to define an operator that takes the product of several expressions, each of which may be passed by reference, reference to const, or rvalue reference. (In my case, the expressions are conditional probability tables and the operation is the factor product, but something like matrix multiplication works suitably as well.) You need access to the data provided by each expression in order to evaluate the product. Consequently, you must move the expressions passed as rvalue references, copy the expressions passed by reference to const, and take the addresses of expressions passed by reference. Using the technique I describe above now poses several benefits. Other expressions can use uniform syntax to access data elements from this expression, since all of the heavy-lifting metaprogramming work is done beforehand, within the class. We can save stack space by grouping the pointers together and storing the larger expressions towards the end of the tuple. Implementing certain types of queries becomes much easier (e.g. check whether any of the pointers stored in the tuple aliases a given pointer). Thank you very much for your help!

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• Using LINQ to isolate a particular obect from a list of objects

  - by dezkev

  Hello All, I am trying my hand at making an invaders clone. there are 30 aliens arranged in a 5x 6 matrix on screen. I need to give the bottom most alien the ability to fire a shot. I am using LINQ to group the aliens into 5 groups based on Location.X and then sort the groups descending.I then need to choose one of the groups ( that gives me 5 groups) and select the First alien in the group and use it;s coordinate to fire a shot. My code below ,well ,works , but aliens in ANY row are merrily firing shots- not just the bottom most. Pl look at my code below and tell me whats wrong. (r = an instance of the Random class, all aliens are in a list called invaders). { var query = (from inv in invaders group inv by inv.Location.X into invgroup orderby invgroup.Key descending select invgroup).ToList(); var invfirst = query[r.Next(query.Count)].First(); invaderShots.Add(new Shot( new Point(invfirst.Area.X + invfirst.Area.Width / 2, invfirst.Area.Y + invfirst.Area.Height + 5), displayrect, Shot.Direction.Down)); }

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• graph and all pairs shortest path in java

  - by Sandra

  I am writing a java program using Flyod-Warshall algorithm “All pairs shortest path”. I have written the following : a0 is the adjacency matrix of my graph, but has infinity instead of 0. vList is the list of vertexes and the cost for each edge is 1. Path[i][j] = k+1 means for going from I to j you first go to k then j int[][] path = new int[size][size]; for(int i = 0; i<path.length;i++) { for(int j = 0; j<path.length; j++) { if(adjM[i][j]==1) path[i][j]=j+1; } } //*************** for (int k = 0; k < vList.size(); k++) for (int i = 0; i < vList.size(); i++) for (int j = 0; j < vList.size(); j++) { if (a0[i][j]>a0[i][k]+ a0[k][j]) path[i][j] = k + 1; a0[i][j] = Math.min(a0[i][j], a0[i][k] + a0[k][j]); } After running this code, in the result a0 is correct, but path is not correct and I don’t know why!. Would you please help me?

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• Porting Perl to C++ `print "\x{2501}" x 12;`

  - by jippie

  I am porting a program from Perl to C++ as a learning objective. I arrived at a routine that draws a table with commands like the following: Perl: print "\x{2501}" x 12; And it draws 12 times a '?' ("box drawings heavy horizontal"). Now I figured out part of the problem already: Perl: \x{}, \x00 Hexadecimal escape sequence; C++: \unnnn To print a single Unicode character: C++: printf( "\u250f\n" ); But does C++ have a smart equivalent for the 'x' operator or would it come down to a for loop? UPDATE Let me include the full source code I am trying to compile with the proposed solution. The compiler does throw an errors: g++ -Wall -Werror project.cpp -o project project.cpp: In function ‘int main(int, char**)’: project.cpp:38:3: error: ‘string’ is not a member of ‘std’ project.cpp:38:15: error: expected ‘;’ before ‘s’ project.cpp:39:3: error: ‘cout’ is not a member of ‘std’ project.cpp:39:16: error: ‘s’ was not declared in this scope #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <string.h> int main ( int argc, char *argv[] ) { if ( argc != 2 ) { fprintf( stderr , "usage: %s matrix\n", argv[0] ); exit( 2 ); } else { //std::string s(12, "\u250f" ); std::string s(12, "u" ); std::cout << s; } }

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• Problem using find function in Matlab

  - by Peter Etchells

  Hi all, I have two arrays of data that I'm trying to amalgamate. One contains actual latencies from an experiment in the first column (e.g. 0.345, 0.455... never more than 3 decimal places), along with other data from that experiment. The other contains what is effectively a 'look up' list of latencies ranging from 0.001 to 0.500 in 0.001 increments, along with other pieces of data. Both data sets are X-by-Y doubles. What I'm trying to do is something like... for i = 1:length(actual_latency) row = find(predicted_data(:,1) == actual_latency(i) full_set(i,1:4) = [actual_latency(i) other_info(i) predicted_info(row,2)... predicted_info(row,3)]; end ...in order to find the relevant row in predicted_data where the look up latency corresponds to the actual latency. I then use this to created an amalgamated data set, full_set. I figured this would be really simple, but the find function keeps failing by throwing up an empty matrix when looking for an actual latency that I know is in predicted_data(:,1) (as I've double-checked during debugging). Moreover, if I replace find with a for loop to do the same job, I get a similar error. It doesn't appear to be systematic - using different participant data sets throws it up in different places. Furthermore, during debugging mode, if I use find to try and find a hard-coded value of actual_latency, it doesn't always work. Sometimes yes, sometimes no. I'm really scratching my head over this, so if anyone has any ideas about what might be going on, I'd be really grateful.

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• Recursion - Ship Battle

  - by rgorrosini

  I'm trying to write a little ship battle game in java. It is 100% academic, I made it to practice recursion, so... I want to use it instead of iteration, even if it's simpler and more efficient in most some cases. Let's get down to business. These are the rules: Ships are 1, 2 or 3 cells wide and are placed horizontally only. Water is represented with 0, non-hit ship cells are 1, hit ship cells are 2 and sunken ships have all it's cells in 3. With those rules set, I'm using the following array for testing: int[][] board = new int[][] { {0, 1, 2, 0, 1, 0}, {0, 0, 1, 1, 1, 0}, {0, 3, 0, 0, 0, 0}, {0, 0, 2, 1, 2, 0}, {0, 0, 0, 1, 1, 1}, }; It works pretty good so far, and to make it more user-friendly I would like to add a couple of reports. these are the methods I need for them: Given the matrix, return the amount of ships in it. Same as a), but separating them by state (amount of non-hit ships, hit and sunken ones). I will need a hand with those reports, and I would like to get some ideas. Remember it must be done using recursion, I want to understand this, and the only way to go is practice! Thanks a lot for your time and patience :).

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• How do I call Matlab in a script on Windows?

  - by Benjamin Oakes

  I'm working on a project that uses several languages: SQL for querying a database Perl/Ruby for quick-and-dirty processing of the data from the database and some other bookkeeping Matlab for matrix-oriented computations Various statistics languages (SAS/R/SPSS) for processing the Matlab output Each language fits its niche well and we already have a fair amount of code in each. Right now, there's a lot of manual work to run all these steps that would be much better scripted. I've already done this on Linux, and it works relatively well. On Linux: matlab -nosplash -nodesktop -r "command" or echo "command" | matlab -nosplash -nodesktop ...opens Matlab in a "command line" mode. (That is, no windows are created -- it just reads from STDIN, executes, and outputs to STDOUT/STDERR.) My problem is that on Windows (XP and 7), this same code opens up a window and doesn't read from / write to the command line. It just stares me blankly in the face, totally ignoring STDIN and STDOUT. How can I script running Matlab commands on Windows? I basically want something that will do: ruby database_query.rb perl legacy_code.pl ruby other_stuff.rb matlab processing_step_1.m matlab processing_step_2.m # etc, etc. I've found out that Matlab has an -automation flag on Windows to start an "automation server". That sounds like overkill for my purposes, and I'd like something that works on both platforms. What options do I have for automating Matlab in this workflow?

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• How to add "missing" columns in a column group in reporting services?

  - by Gimly

  Hello, I'm trying to create a report that displays for each months of the year the quantity of goods sold. I have a query that returns the list of goods sold for each month, it looks something like this : SELECT Seller.FirstName, Seller.LastName, SellingHistory.Month, SUM(SellingHistory.QuantitySold) FROM SellingHistory JOIN Seller on SellingHistory.SellerId = Seller.SellerId WHERE SellingHistory.Year = @Year GOUP BY Seller.FirstName, Seller.LastName, SellingHistory.Month What I want to do is display a report that has a column for each months + a total column that will display for each Seller the quantity sold in the selected month. Seller Name | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total What I managed to do is using a matrix and a column group (group on Month) to display the columns for existing data, if I have data from January to March, it will display the 3 first columns and the total. What I would like to do is always display all the columns. I thought about making that by adding the missing months in the SQL request, but I find that a bit weird and I'm sure there must be some "cleanest" solution as this is something that must be quite frequent. Thanks. PS: I'm using SQL Server Express 2008

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• Getting the current item number or index when using will_paginate in rails app

  - by Rich

  I have a rails app that stores movies watched, books read, etc. The index page for each type lists paged collections of all its items, using will_paginate to bring back 50 items per page. When I output the items I want to display a number to indicate what item in the total collection it is. The numbering should be reversed as the collection is displayed with most recent first. This might not relate to will_paginate but rather some other method of calculation. I will be using the same ordering in multiple types so it will need to be reusable. As an example, say I have 51 movies. The first item of the first page should display: Fight Club - Watched: 30th Dec 2010 Whilst the last item on the page should display: The Matrix - Watched: 3rd Jan 2010 The paged collection is available as an instance variable e.g. @movies, and @movies.count will display the number of items in the paged collection. So if we're on page 1, movies.count == 50, whilst on page 2 @movies.count == 1. Using Movie.count would give 51. If the page number and page size can be accessed the number could be calculated so how can they be returned? Though I'm hopeful there is something that already exists to handle this calculation!

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• Boolean comparison of array of strings in Ruby

  - by Kyle Kaitan

  I've got an array in Ruby that essentially represents a square boolean matrix. Dots represent zeroes, while any other character represents ones. Example: irb(main):044:0> g => [".b", "m."] # This grid has two '1' values and two '0' values. I'd like to perform a specified logical operation (say, OR) on this array with another similar array to get a third result. For example, if h is ["q.", "r."], then something akin to g.perform_or(h) should yield a new array ["qb", "r."]. (The choice of r to represent the result of 'm' || 'r' is arbitrary and not relevant; any other non-'.' character can be there.) How might I do this? Edit: I made an error in my example. Apologies!

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• How to reapper the sphere shape of SVG tag code by Raphael description exactly?

  - by TelTel

  I'm trying to figure a Raphael.js shape(sphere) which is based on following SVG tag code. I have succeed in basic similar sphere style by the description : Paper.circle(100, 100, 30).attr({ fill: "r(0.35, 0.25)#FFFFFF-#252525:96-#000000", stroke: "none"}); // radius is 30 But I can't reappear exactly. --- [picture] ** The tag code of sphere ... main part is extracted ** <g id="layer1"> <radialGradient id="path5725_3_" cx="156.0352" cy="657.6802" r="200.0004" gradientTransform="matrix(1.0404 0.7962 0.8145 -1.0643 -531.7884 745.2471)" gradientUnits="userSpaceOnUse"> <stop offset="0" style="stop-color:#FFFFFF"/> <stop offset="1" style="stop-color:#000000"/> </radialGradient> <path id="path5725" fill="url(#path5725_3_)" d="M445.037,229.105c0,113.218-89.543,205-200,205c-110.457, 0-200-91.782-200-205s89.543-205,200-205C355.494, 24.105,445.037,115.887,445.037,229.105z"/> </g> ** ---------------------------------------- ** Here the completed picture of tag code is linked. How to describe(modify) the Raphael.js code to reappear the picture ? Thank you.

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• Outer product using CBLAS

  - by The Dude

  I am having trouble utilizing CBLAS to perform an Outer Product. My code is as follows: //===SET UP===// double x1[] = {1,2,3,4}; double x2[] = {1,2,3}; int dx1 = 4; int dx2 = 3; double X[dx1 * dx2]; for (int i = 0; i < (dx1*dx2); i++) {X[i] = 0.0;} //===DO THE OUTER PRODUCT===// cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasTrans, dx1, dx2, 1, 1.0, x1, dx1, x2, 1, 0.0, X, dx1); //===PRINT THE RESULTS===// printf("\nMatrix X (%d x %d) = x1 (*) x2 is:\n", dx1, dx2); for (i=0; i<4; i++) { for (j=0; j<3; j++) { printf ("%lf ", X[j+i*3]); } printf ("\n"); } I get: Matrix X (4 x 3) = x1 (*) x2 is: 1.000000 2.000000 3.000000 0.000000 -1.000000 -2.000000 -3.000000 0.000000 7.000000 14.000000 21.000000 0.000000 But the correct answer is found here: https://www.sharcnet.ca/help/index.php/BLAS_and_CBLAS_Usage_and_Examples I have seen: Efficient computation of kronecker products in C But, it doesn't help me because they don't actually say how to utilize dgemm to actually do this... Any help? What am I doing wrong here?

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• Populate array from vector

  - by Zag zag..

  Hi, I would like to populate an 2 dimensional array, from a vector. I think the best way to explain myself is to put some examples (with a array of [3,5] length). When vector is: [1, 0] [ [4, 3, 2, 1, 0], [4, 3, 2, 1, 0], [4, 3, 2, 1, 0] ] When vector is: [-1, 0] [ [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4] ] When vector is: [-2, 0] [ [0, 0, 1, 1, 2], [0, 0, 1, 1, 2], [0, 0, 1, 1, 2] ] When vector is: [1, 1] [ [2, 2, 2, 1, 0], [1, 1, 1, 1, 0], [0, 0, 0, 0, 0] ] When vector is: [0, 1] [ [2, 2, 2, 2, 2], [1, 1, 1, 1, 1], [0, 0, 0, 0, 0] ] Have you got any ideas, a good library or a plan? Any comments are welcome. Thanks. Note: I consulted Ruby "Matrix" and "Vector" classes, but I don't see any way to use it in my way... Edit: In fact, each value is the number of cells (from the current cell to the last cell) according to the given vector. If we take the example where the vector is [-2, 0], with the value *1* (at array[2, 3]): array = [ [<0>, <0>, <1>, <1>, <2>], [<0>, <0>, <1>, <1>, <2>], [<0>, <0>, <1>, *1*, <2>] ] ... we could think such as: The vector [-2, 0] means that -2 is for cols and 0 is for rows. So if we are in array[2, 3], we can move 1 time on the left (left because 2 is negative) with 2 length (because -2.abs == 2). And we don't move on the top or bottom, because of 0 for rows.

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• 3x3 array = 10 numbers

  - by user1708505

  i have this code #include <math.h> #include <stdio.h> const int n = 3; const int s = 3; int getm(int mat[n][s]); int printm(int mat[n][s]); int main() { int m[n][s]; getm(m); printm(m); return 0; } int getm(int mat[n][s]) { for(int x = 0;x < n;x++) { for (int y = 0;y<s;y++) { scanf("%i ", &mat[x][y]); } } return 0; } int printm(int mat[n][s]) { for(int x = 0;x<n;x++) { for(int y = 0;y<s;y++) { printf("%i ", mat[x][y]); if(y==(s-1)) { printf("\n"); } } } } which shoud ask for 9 numbers to make a 3x3 matrix array, but it actually asks for 10 numbers, printm is working well - printing only 9 numbers. Where is error?

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• faster way to compare rows in a data frame

  - by aguiar

  Consider the data frame below. I want to compare each row with rows below and then take the rows that are equal in more than 3 values. I wrote the code below, but it is very slow if you have a large data frame. How could I do that faster? data <- as.data.frame(matrix(c(10,11,10,13,9,10,11,10,14,9,10,10,8,12,9,10,11,10,13,9,13,13,10,13,9), nrow=5, byrow=T)) rownames(data)<-c("sample_1","sample_2","sample_3","sample_4","sample_5") >data V1 V2 V3 V4 V5 sample_1 10 11 10 13 9 sample_2 10 11 10 14 9 sample_3 10 10 8 12 9 sample_4 10 11 10 13 9 sample_5 13 13 10 13 9 tab <- data.frame(sample = NA, duplicate = NA, matches = NA) dfrow <- 1 for(i in 1:nrow(data)) { sample <- data[i, ] for(j in (i+1):nrow(data)) if(i+1 <= nrow(data)) { matches <- 0 for(V in 1:ncol(data)) { if(data[j,V] == sample[,V]) { matches <- matches + 1 } } if(matches > 3) { duplicate <- data[j, ] pair <- cbind(rownames(sample), rownames(duplicate), matches) tab[dfrow, ] <- pair dfrow <- dfrow + 1 } } } >tab sample duplicate matches 1 sample_1 sample_2 4 2 sample_1 sample_4 5 3 sample_2 sample_4 4

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• UserControlArray in Specific ButtonControlArray in C#

  - by Phanindar

  I am new to C#.I have been thinking of adding a ButtonControlArray where i can store each button control.Here is part of my code.I am creating a 6*6 array of button Control. ButtonControl buttonControl; ButtonControl[,] arrayButtons = new ButtonControl[6,6]; public void createGrid() { l = 0; for (int i = 0; i < numberOfButtons; i++) { for (int k = 0; k < numberOfButtons; k++) { buttonControl = new ButtonControl(); buttonControl.Location = new Point(l,j); j += 55; arrayButtons[i, k] = buttonControl; //After the above statement if i print Console.WriteLine(""+arrayButtons[i,k]); i am getting only my projectname.buttoncontrol myGridControl.Controls.Add(buttonControl); } l += 55; j = 10; } } I want to access each variable in arrayButtons[][]..like in a 3*3 matrix..if i want 2nd row 1 column element..then i get something like arrayname[2][1]..same way if i want 2nd button in 2nd row how can i get..i tried doing one way but i couldnt figure it out...Can you help me out with this..

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• Populating a color array with every 8th pixel in an image. C#

  - by Piper

  I have an image that is 512x280 pixels. I want to populate a 64x35 array with every 8th pixel in the matrix. Here is what I have right now: Color[,] imgArray = new Color[b.Width, b.Height]; for (int y = 0; y < 35; y++) { for (int x = 0; x < 64; x++) { imgArray[x, y] = b.GetPixel(x, y); } } But that will get just the top corner of the image. How would I change the loop so it grabs every 8th pixel to fill the array with? edit: I think I may have gotten it. Can someone read this and assure me that it is correct? Color[,] imgArray = new Color[64, 35]; for (int y = 0; y < 280; y+=8) { for (int x = 0; x < 512; x+=8) { imgArray[x, y] = b.GetPixel(x, y); } }

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