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• MATLAB using MAT2CELL

  - by Ali

  i have the following matrices letter=[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ... a b c d e f g h ii jj k l m o p q r s t u v w x y z]; number=[one two three four five six seven eight nine zero]; character =[number letter]; Character becomes a matrix of 42 by 1464, but i would like to break it into cells of 42 by 24 using mat2cell. How can i please do it, every time i try i get an error????

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• Representing Sparse Data in PostgreSQL

  - by Chris S

  What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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• Is Matlab faster than Python?

  - by kame

  I want to compute magnetic fields of some conductors using the biot-savart-law and I want to use a 1000x1000x1000 matrix. Before I use Matlab, but now I want to use Python. Is Python slower than Matlab? How can I make Python faster? EDIT: Maybe the best way is to compute the big array with c/c++ and then transfering them to python. I want to visualise then with VPython. EDIT2: Could somebody give an advice for which is better in my case: C or C++?

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• How to get predecessor and successors from an adjacency matrix

  - by NickTFried

  Hi I am am trying to complete an assignment, where it is ok to consult the online community. I have to create a graph class that ultimately can do Breadth First Search and Depth First Search. I have been able to implement those algorithms successfully however another requirement is to be able to get the successors and predecessors and detect if two vertices are either predecessors or successors for each other. I'm having trouble thinking of a way to do this. I will post my code below, if anyone has any suggestions it would be greatly appreciated. import java.util.ArrayList; import java.util.Iterator; import java.util.LinkedList; import java.util.Queue; import java.util.Stack; public class Graph<T> { public Vertex<T> root; public ArrayList<Vertex<T>> vertices=new ArrayList<Vertex<T>>(); public int[][] adjMatrix; int size; private ArrayList<Vertex<T>> dfsArrList; private ArrayList<Vertex<T>> bfsArrList; public void setRootVertex(Vertex<T> n) { this.root=n; } public Vertex<T> getRootVertex() { return this.root; } public void addVertex(Vertex<T> n) { vertices.add(n); } public void removeVertex(int loc){ vertices.remove(loc); } public void addEdge(Vertex<T> start,Vertex<T> end) { if(adjMatrix==null) { size=vertices.size(); adjMatrix=new int[size][size]; } int startIndex=vertices.indexOf(start); int endIndex=vertices.indexOf(end); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public void removeEdge(Vertex<T> v1, Vertex<T> v2){ int startIndex=vertices.indexOf(v1); int endIndex=vertices.indexOf(v2); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public int countVertices(){ int ver = vertices.size(); return ver; } /* public boolean isPredecessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ /* public boolean isSuccessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ public void getSuccessors(Vertex<T> v1){ } public void getPredessors(Vertex<T> v1){ } private Vertex<T> getUnvisitedChildNode(Vertex<T> n) { int index=vertices.indexOf(n); int j=0; while(j<size) { if(adjMatrix[index][j]==1 && vertices.get(j).visited==false) { return vertices.get(j); } j++; } return null; } public Iterator<Vertex<T>> bfs() { Queue<Vertex<T>> q=new LinkedList<Vertex<T>>(); q.add(this.root); printVertex(this.root); root.visited=true; while(!q.isEmpty()) { Vertex<T> n=q.remove(); Vertex<T> child=null; while((child=getUnvisitedChildNode(n))!=null) { child.visited=true; bfsArrList.add(child); q.add(child); } } clearVertices(); return bfsArrList.iterator(); } public Iterator<Vertex<T>> dfs() { Stack<Vertex<T>> s=new Stack<Vertex<T>>(); s.push(this.root); root.visited=true; printVertex(root); while(!s.isEmpty()) { Vertex<T> n=s.peek(); Vertex<T> child=getUnvisitedChildNode(n); if(child!=null) { child.visited=true; dfsArrList.add(child); s.push(child); } else { s.pop(); } } clearVertices(); return dfsArrList.iterator(); } private void clearVertices() { int i=0; while(i<size) { Vertex<T> n=vertices.get(i); n.visited=false; i++; } } private void printVertex(Vertex<T> n) { System.out.print(n.label+" "); } }

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• More complex view matrix calculation required to composite 3d models with 2d video

  - by lzcd

  I'm utilising some 2d / 3d tracking data (provided by pfHoe) to help integrate some 3d models into the playback of some 2d video. Things are working.... okay... but there's still some visible 'slipping' of the models against the video background and I suspect this is may be because the XNA CreatePerspective helper method isn't taking into account some of the additional data supplied by pfHoe such as independent horizontal / vertical field of view angles and focal length. Would anyone be able to point me towards some examples of constructing view matrices that include such details?

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• Generate quantization matrix

  - by Bass

  Hello, how can i generate quantizatinon metrices with diffrent size and quality, is there a function in matlab for this?

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• MATLAB (MATrix LABoratory) interview questions?

  - by Shane

  I programmed in Matlab for many years, but switched to using R exclusively in the past few years so I'm a little out of practice. I'm interviewing a candidate today who describes himself as a Matlab expert. What MATLAB interview questions that I should be asking?

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• How to use Eclipse and versioning for a matrix of projects

  - by Nulldevice

  Our company develop several software products, which reuse each others packages (we use Java). Every product represented as separate Eclipse Java project and has it's own versioning repository (we use Mercurial). When we find a bug in some shared package, we need to transfer changes to all consuming projects, and this is a hell. The key problem is that Eclipse project can be associated only with one versioning repository. Could someone recommend some way to associate Eclipse Java project whith several versioning repositories which in ideal may be geterogeious (svn, git, mercurial) ?

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• How to set orthgraphic matrix for a 2d camera with zooming?

  - by MahanGM

  I'm using ID3DXSprite to draw my sprites and haven't set any kind of camera projection matrix. How to setup an orthographic projection matrix for camera in DirectX which it would be able to support zoom functionality? D3DXMATRIX orthographicMatrix; D3DXMATRIX identityMatrix; D3DXMatrixOrthoLH(&orthographicMatrix, nScreenWidth, nScreenHeight, 0.0f, 1.0f); D3DXMatrixIdentity(&identityMatrix); device->SetTransform(D3DTS_PROJECTION, &orthographicMatrix); device->SetTransform(D3DTS_WORLD, &identityMatrix); device->SetTransform(D3DTS_VIEW, &identityMatrix); This code is for initial setup. Then, for zooming I multiply zoom factor in nScreenWidth and nScreenHeight.

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• Operating on rows and then on columns of a matrix produces code duplication

  - by Chetan

  I have the following (Python) code to check if there are any rows or columns that contain the same value: # Test rows -> # Check each row for a win for i in range(self.height): # For each row ... firstValue = None # Initialize first value placeholder for j in range(self.width): # For each value in the row if (j == 0): # If it's the first value ... firstValue = b[i][j] # Remember it else: # Otherwise ... if b[i][j] != firstValue: # If this is not the same as the first value ... firstValue = None # Reset first value break # Stop checking this row, there's no win here if (firstValue != None): # If first value has been set # First value placeholder now holds the winning player's code return firstValue # Return it # Test columns -> # Check each column for a win for i in range(self.width): # For each column ... firstValue = None # Initialize first value placeholder for j in range(self.height): # For each value in the column if (j == 0): # If it's the first value ... firstValue = b[j][i] # Remember it else: # Otherwise ... if b[j][i] != firstValue: # If this is not the same as the first value ... firstValue = None # Reset first value break # Stop checking this column, there's no win here if (firstValue != None): # If first value has been set # First value placeholder now holds the winning player's code return firstValue # Return it Clearly, there is a lot of code duplication here. How do I refactor this code? Thanks!

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• What do gurus say about Requirements Traceability Matrix?

  - by Jaywalker

  Our organization is at CMMI Level 2, and as part of the requirements of the level, we have to maintain an RTM which more or less contains the following entries for each requirement: Requirement Description Reference Section Functional Specification Document Reference Section Design Document Reference Section Test Cases Document Now, this might be an overkill for a small project. But more importantly, this could be a nightmare to maintain when the requirements/ features keep changing, and documents have to be constantly updated. What do the gurus say about this? Should one avoid such level of documentation or are there any tools to manage when a "change" out dates so many artifacts? And by using the term 'gurus', I am not talking of coding champs; rather people like Steve McConnel or others who have worked on commercial projects of medium to large scale. Quotes/ book references/ articles will suit me. EDIT: It's not just requirements that change. Design Document can change; well, even test cases may change.

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• Models from 3ds max lose their transformations when input into XNA

  - by jacobian

  I am making models in 3ds max. However when I export them to .fbx format and then input them into XNA, they lose their scaling. -It is most likely something to do with not using the transforms from the model correctly, is the following code correct -using xna 3.0 Matrix[] transforms=new Matrix[playerModel.Meshes.Count]; playerModel.CopyAbsoluteBoneTransformsTo(transforms); // Draw the model. int count = 0; foreach (ModelMesh mesh in playerModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = transforms[count]* Matrix.CreateScale(scale) * Matrix.CreateRotationX((float)MathHelper.ToRadians(rx)) * Matrix.CreateRotationY((float)MathHelper.ToRadians(ry)) * Matrix.CreateRotationZ((float)MathHelper.ToRadians(rz))* Matrix.CreateTranslation(position); effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } count++; mesh.Draw(); }

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• deteminant of matrix

  - by davit-datuashvili

  suppose there is given two dimensional array int a[][]=new int[4][4]; i am trying to find determinant of matrices please help i know how find it mathematical but i am trying to find it in programaticaly

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• WinForm resizing matrix?

  - by serhio

  WinForms question: Is there a way to keep elements at a proportional distance when the parent form(or panel) is resized?

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• transforming 1d (1column) into 5d(5column) matrix through copy paste or other

  - by Curious

  Ex. I want to take the column with 12345..... and order 5 columns across as seen. next 5 numbers in column will be next row. However my code creates a 4 row gap in between each successive row. I dont know what additional logic (possibly if then statement) I can embed into do loop to may make it cleaner. I am new to this, so showing as much sample code to learn the syntax would be most beneficial. thanks in advance. Below is the Result of my code. VBA code is below result. 1 1 2 3 4 5 2 3 4 5 6 6 7 8 9 10 7 8 9 10 11 11 12 13 14 15 12 13 14 15 16 16 17 17 Sub Working_Code() ' Working_Code Macro Do ActiveCell.Select Selection.Copy ActiveCell.Offset(0, 5).Select ActiveSheet.Paste ActiveCell.Offset(1, -5).Select Selection.Copy ActiveCell.Offset(-1, 6).Select ActiveSheet.Paste ActiveCell.Offset(2, -6).Select Selection.Copy ActiveCell.Offset(-2, 7).Select ActiveSheet.Paste ActiveCell.Offset(3, -7).Select Selection.Copy ActiveCell.Offset(-3, 8).Select ActiveSheet.Paste ActiveCell.Offset(4, -8).Select Selection.Copy ActiveCell.Offset(-4, 9).Select ActiveSheet.Paste ActiveCell.Offset(5, -9).Select Loop Until IsEmpty(ActiveCell.Offset(0, -1)) End Sub

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• 2D pixel array rotation and scaling

  - by Betamoo

  Hi I am working on C# program to process images ( given as int[,] ).. So I have 2D array of pixels, and I need to rotate them around a point, then scale them down to fit the original array.. I already found articles about using matrix to transform to a point and rotate then transform back.. What remains is to scale the resultant image to fit an array of original size.. How that can be done? (preferably with 2 equations one for x and one for y ) Thanks in advance

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• ILNumerics multiply complex with matrix<double>

  - by nik

  I m looking at ILNumerics to translate some matlab code into c#. How would I multiply a complex and a double? Simplified description: In Matlab: A=[1 2 3] i*A*A' Returns a complex number. How would I do the same in ILNumerics: ILArray<double> A = ILMath.array(1.0, 2.0, 3.0); complex B = complex.i * ILMath.multiply(A,A.T); Throws the error: Operator '*' cannot be applied to operands of type 'ILNumerics.complex' and 'ILNumerics.ILRetArray<double>' Update This works: double C = 14.0; complex D = complex.i * C; But shouldnt: ILMath.multiply(A,A.T) also return 14.0?

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• Error " Index exceeds Matrix dimensions"

  - by Mola

  Hi experts, I am trying to read an excel 2003 file which consist of 62 columns and 2000 rows and then draw 2d dendrogram from 2000 pattern of 2 categories of a data as my plot in matlab. When i run the script, it gives me the above error. I don't know why. Anybody has any idea why i have the above error? My data is here: http://rapidshare.com/files/383549074/data.xls Please delete the 2001 column if you want to use the data for testing. and my code is here: % Script file: cluster_2d_data.m d=2000; n1=22; n2=40; N=62 Data=xlsread('data.xls','A1:BJ2000'); X=Data'; R=1:2000; C=1:2; clustergram(X,'Pdist','euclidean','Linkage','complete','Dimension',2,... 'ROWLABELS',R,'COLUMNLABELS',C,'Dendrogram',{'color',5})

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• Indexing one-dimensional numpy.array as matrix

  - by Alain

  I am trying to index a numpy.array with varying dimensions during runtime. To retrieve e.g. the first row of a n*m array a, you can simply do a[0,:] However, in case a happens to be a 1xn vector, this code above returns an index error: IndexError: too many indices As the code needs to be executed as efficiently as possible I don't want to introduce an if statement. Does anybody have a convenient solution that ideally doesn't involve changing any data structure types?

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• printf'ing a matrix

  - by Flavius

  I'm trying to implement an all-purpose function for printing 2D data. What I've come up with is: int mprintf(FILE* f, char* fmt, void** data, size_t cols, size_t rows) The challenge is determining how many bits to read at once from data, based on fmt. The format fmt is going to be the stdlib's-specific format for printf() and alike. Do you have any knowledge of already-existing features from stdlibc (GNU GCC C's) I could use to ease this up? I try avoiding having to do it all manually, because I know "I am stupid" (I don't want to introduce stupid bugs). Thus, reusing code would be the bug-freest way. Thanks Addendum I see there's a /usr/include/printf.h. Can't I use any of those functions to do it right and ease my job at the same time?

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• Help Please, I want use LINQ to Query Count in a matrix according to a array!

  - by Bob Feng

  I have a matrix, IEnumerable<IEnumerable<int>> matrix, for example: { {10,23,16,20,2,4}, {22,13,1,33,21,11 }, {7,19,31,12,6,22}, ... } and another array: int[] arr={ 10, 23, 16, 20} I want to filter the matrix on the condition that I group all rows of the matrix which contain the same number of elements from arr. That is to say the first row in the matrix {10,23,16,20,2,4} has 4 numbers from arr, this array should be grouped with the rest of the rows with 4 numbers from arr. better to use linq, thank you very much!

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• i want to multiply a character L to identity matrix in c#

  - by vj4u

  for (int row = 0; row < SS; row++) { for (int col = 0; col < SS; col++) { identity[row, col] = (row == col) ? 1 : 0; Response.Write(identity[row, col] + " "); } Response.Write("<br/>"); } now my output is 1 0 0 0 1 0 0 0 1 i want to get output as L 0 0 0 L 0 0 0 L

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• Twisted Matrix and telnet server implementation

  - by ypercube

  I have a project which is essentially a game server where users connect and send text commands via telnet. The code is in C and really old and unmodular and has several bugs and missing features. The main function alone is half the code. I came to the conclusion that rewriting it in TwistedMachine could actually result in faster completement, besides other benefits. So, here is the questions: What packages and modules I should use? I see a "telnet" module inside "protocols" package. I also see "cronch" package with "ssh" and another "telnet" module. I'm a complete novice regarding Python.

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• How to create a matrix format in perl

  - by shaq

  I have an array of array in which each array is like: clusterA gene1 1 clusterA gene2 0 clusterB gene1 1 clusterB gene2 0 I want to produce a file like: name gene1 gene2 clusterA 1 0 clusterB 1 0 Current attempt: if (condition) { @array = ($cluster, $genes, "1"); } elsif (not condition) { @array = ($cluster, $genes, "0"); } push @AoA, [ @array ]; @A0A is my array of array.

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• Improve C function performance with cache locality?

  - by Christoper Hans

  I have to find a diagonal difference in a matrix represented as 2d array and the function prototype is int diagonal_diff(int x[512][512]) I have to use a 2d array, and the data is 512x512. This is tested on a SPARC machine: my current timing is 6ms but I need to be under 2ms. Sample data: [3][4][5][9] [2][8][9][4] [6][9][7][3] [5][8][8][2] The difference is: |4-2| + |5-6| + |9-5| + |9-9| + |4-8| + |3-8| = 2 + 1 + 4 + 0 + 4 + 5 = 16 In order to do that, I use the following algorithm: int i,j,result=0; for(i=0; i<4; i++) for(j=0; j<4; j++) result+=abs(array[i][j]-[j][i]); return result; But this algorithm keeps accessing the column, row, column, row, etc which make inefficient use of cache. Is there a way to improve my function?

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