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  • Understanding this matrix transposition function in Haskell

    - by dmindreader
    This matrix transposition function works, but I'm trying to understand its step by step execurtion and I don't get it. transpose:: [[a]]->[[a]] transpose ([]:_) = [] transpose x = (map head x) : transpose (map tail x) with transpose [[1,2,3],[4,5,6],[7,8,9]] it returns: [[1,4,7],[2,5,8],[3,6,9]] I don't get how the concatenation operator is working with map. It is concatenating each head of x in the same function call? How?

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  • Is there an Open Source licence matrix?

    - by tobsen
    I am trying to find a simple matrix overview of the various licenses around open source software but can't find anything useful. I would like to know whether software under a certain licence can be used in commercial closed source software, if there has to be the original source code included, if the licence has to be redistirbuted, etc. I know this is a difficult topic because I guess only the minority of programmers are also moonlighting lawyers - neither am I.

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  • OpenGL: Implementing transformation matrix stack

    - by Jakub M.
    In a newer OpenGL there is no matrix stack. I am working on a simple display engine, and I am going to implement the transformation stack. What is a common strategy here? Should I build a push/pop stack, and use it with a tree representing my model? I suppose this is the "old" approach, that was deprecated in the newer OpenGL versions. Maybe then it is not the best solution (it was removed for some reason)

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  • To find a determinate of Matrix using Boost library in c++

    - by user314097
    Hi, I' am required to convert a MATLAB function into C++, and this requires me to find determinate of a matrix. I was told that use of BOOST library would make my job easier. I went through the documentation of BOOST Library, but couldn't find much info about the same. If anyone could give a template for the above operation, It would be of lot of help and would be greatly appreciated. Thanks Regards

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  • Using rowDiffs() to calculate difference in values in matrix

    - by user1723765
    I'm using the rowDiffs() command to calculate the step by step difference in 116 rows in a matrix. I get the following error: Error in r[i1] - r[-length(r):-(length(r) - lag + 1L)] : non-numeric argument to binary operator I have no idea why this is happening. I could take the diff() separately for each row and it would work. Any ideas? Here's the data: https://dl.dropbox.com/u/22681355/data.csv Code: a=rowDiffs(data)

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  • Is this overly clever or unsafe?

    - by Liberalkid
    I was working on some code recently and decided to work on my operator overloading in c++, because I've never really implemented it before. So I overloaded the comparison operators for my matrix class using a compare function that returned 0 if LHS was less than RHS, 1 if LHS was greater than RHS and 2 if they were equal. Then I exploited the properties of logical not in c++ on integers, to get all of my compares in one line: inline bool Matrix::operator<(Matrix &RHS){ return ! (compare(*this,RHS)); } inline bool Matrix::operator>(Matrix &RHS){ return ! (compare((*this),RHS)-1); } inline bool Matrix::operator>=(Matrix &RHS){ return compare((*this),RHS); } inline bool Matrix::operator<=(Matrix &RHS){ return compare((*this),RHS)-1; } inline bool Matrix::operator!=(Matrix &RHS){ return compare((*this),RHS)-2; } inline bool Matrix::operator==(Matrix &RHS){ return !(compare((*this),RHS)-2); } Obviously I should be passing RHS as a const, I'm just probably not going to use this matrix class again and I didn't feel like writing another function that wasn't a reference to get the array index values solely for the comparator operation.

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  • computing matting Laplacian matrix of an Image

    - by ajith
    hi everyone, i need to compute Laplacian Matrix-L for an image(nXn) in opencv...computing goes as follows.......... dij - 1/|wk|{[1+1/(e/|wk|+s2)][(Ii-µk)*(Ij -µk)]}.... for all(i,j)?wk,summing over k yields (i,j)th element of L. where Here dij is the Kronecker delta,µk and s2k are the mean & variance of intensities in the window wk around k,and |wk| is the number of pixels in this window.wk is 3X3 window... here am not clear about 2 things... 1.what ll be the size of L?nXn or (nXn)X(nXn)?? 2.how to select Ii and Ij separately in 2D image?

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  • Vectorizatoin of index operation for a scipy.sparse matrix

    - by celil
    The following code runs too slowly even though everything seems to be vectorized. from numpy import * from scipy.sparse import * n = 100000; i = xrange(n); j = xrange(n); data = ones(n); A=csr_matrix((data,(i,j))); x = A[i,j] The problem seems to be that the indexing operation is implemented as a python function, and invoking A[i,j] results in the following profiling output 500033 function calls in 8.718 CPU seconds Ordered by: internal time ncalls tottime percall cumtime percall filename:lineno(function) 100000 7.933 0.000 8.156 0.000 csr.py:265(_get_single_element) 1 0.271 0.271 8.705 8.705 csr.py:177(__getitem__) (...) Namely, the python function _get_single_element gets called 100000 times which is really inefficient. Why isn't this implemented in pure C? Does anybody know of a way of getting around this limitation, and speeding up the above code? Should I be using a different sparse matrix type?

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  • JAVA: Sort ArrayList<ArrayList<Integer>> on multiple columns

    - by Bob
    First, I did do my homework searching before posting here. My requirement seems to be slightly different compared to questions posted out there. I have a matrix like ArrayList<ArrayList<Integer>> in the following form | id1 | id2 | score | |-----|-----|-------| | 1 | 3 | 95% | | 1 | 2 | 100% | | 1 | 4 | 85% | | 1 | 5 | 95% | | 2 | 10 | 80% | | 2 | 15 | 99% | I want to sort the matrix column-wise (first using score, then the id1). I already have the id1 in a sorted manner. That means I also need to sort all records with the same id1 first by using score, second by the id2. The reason for doing this is to create a ranking of the id2 in each id1. The result for the above example would be: | q_id | d_id | rank | score | |------|------|------|-------| | 1 | 2 | 1 | 100% | | 1 | 3 | 2 | 95% | | 1 | 5 | 3 | 95% | | 1 | 4 | 4 | 85% | | 2 | 15 | 1 | 99% | | 2 | 10 | 2 | 80% | How can I achieve this in Java using some built-in methods of collections?

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  • Smooth animation using MatrixTransform?

    - by Mattias Konradsson
    I'm trying to do an Matrix animation where I both scale and transpose a canvas at the same time. The only approach I found was using a MatrixTransform and MatrixAnimationUsingKeyFrames. Since there doesnt seem to be any interpolation for matrices built in (only for path/rotate) it seems the only choice is to try and build the interpolation and DiscreteMatrixKeyFrame's yourself. I did a basic implementation of this but it isnt exactly smooth and I'm not sure if this is the best way and how to handle framerates etc. Anyone have suggestions for improvement? Here's the code: MatrixAnimationUsingKeyFrames anim = new MatrixAnimationUsingKeyFrames(); int duration = 1; anim.KeyFrames = Interpolate(new Point(0, 0), centerPoint, 1, factor,100,duration); this.matrixTransform.BeginAnimation(MatrixTransform.MatrixProperty, anim,HandoffBehavior.Compose); public MatrixKeyFrameCollection Interpolate(Point startPoint, Point endPoint, double startScale, double endScale, double framerate,double duration) { MatrixKeyFrameCollection keyframes = new MatrixKeyFrameCollection(); double steps = duration * framerate; double milliSeconds = 1000 / framerate; double timeCounter = 0; double diffX = Math.Abs(startPoint.X- endPoint.X); double xStep = diffX / steps; double diffY = Math.Abs(startPoint.Y - endPoint.Y); double yStep = diffY / steps; double diffScale= Math.Abs(startScale- endScale); double scaleStep = diffScale / steps; if (endPoint.Y < startPoint.Y) { yStep = -yStep; } if (endPoint.X < startPoint.X) { xStep = -xStep; } if (endScale < startScale) { scaleStep = -scaleStep; } Point currentPoint = new Point(); double currentScale = startScale; for (int i = 0; i < steps; i++) { keyframes.Add(new DiscreteMatrixKeyFrame(new Matrix(currentScale, 0, 0, currentScale, currentPoint.X, currentPoint.Y), KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(timeCounter)))); currentPoint.X += xStep; currentPoint.Y += yStep; currentScale += scaleStep; timeCounter += milliSeconds; } keyframes.Add(new DiscreteMatrixKeyFrame(new Matrix(endScale, 0, 0, endScale, endPoint.X, endPoint.Y), KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(0)))); return keyframes; }

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  • Mat matrix multiplication, openCV?

    - by facebook-1593205594
    I initialized two Mat images as: Mat ft=Mat::zeros(src.rows,src.cols,CV_32FC1),h=Mat::zeros(src.rows,src.cols,CV_32FC1); and then i have some calculations: ft has fourier transform stored for an image, and h has matrix for Laplacian filtering in fourier domain.......they both have same dimensions, and then i did multiplication of them using both h*ft and gemm(h,ft,1,NULL,0,temp); function call but while executing it shows some problems..... it reads like this: opencv error assertion failed (some long code and at last says something about gemm in ....matmul.cpp)......termination called after throwing exception of 'cv::exception'

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  • How to stringfy a swig matrix object in python

    - by leo
    Hi, I am using swig wrapper of openbabel(written in C++, and supply a python wrapper through swig) Below i just use it to read a molecule structure file and get the unitcell property of it. import pybel for molecule in pybel.readfile('pdb','./test.pdb'): unitcell = molecule.unitcell print unitcell |.. |.. The unitcell has function CellMatrix(), unitcell.GetCellMatrix() <22 the OpenBabel::matrix3x3 is something like : 1 2 3 4 5 6 7 8 9 i am wondering how to print out the contents of the matrix3*3 . I have tried str and repr with it. Any general way to stringfy the contents of a matrix wrapped by swing in python ? thanks

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  • How to find vector for the quaternion from X Y Z rotations

    - by can poyrazoglu
    I am creating a very simple project on OpenGL and I'm stuck with rotations. I am trying to rotate an object indepentdently in all 3 axes: X, Y, and Z. I've had sleepless nights due to the "gimbal lock" problem after rotating about one axis. I've then learned that quaternions would solve my problem. I've researched about quaternions and implementd it, but I havent't been able to convert my rotations to quaternions. For example, if I want to rotate around Z axis 90 degrees, I just create the {0,0,1} vector for my quaternion and rotate it around that axis 90 degrees using the code here: http://iphonedevelopment.blogspot.com/2009/06/opengl-es-from-ground-up-part-7_04.html (the most complicated matrix towards the bottom) That's ok for one vector, but, say, I first want to rotate 90 degrees around Z, then 90 degrees around X (just as an example). What vector do I need to pass in? How do I calculate that vector. I am not good with matrices and trigonometry (I know the basics and the general rules, but I'm just not a whiz) but I need to get this done. There are LOTS of tutorials about quaternions, but I seem to understand none (or they don't answer my question). I just need to learn to construct the vector for rotations around more than one axis combined. UPDATE: I've found this nice page about quaternions and decided to implement them this way: http://www.cprogramming.com/tutorial/3d/quaternions.html Here is my code for quaternion multiplication: void cube::quatmul(float* q1, float* q2, float* resultRef){ float w = q1[0]*q2[0] - q1[1]*q2[1] - q1[2]*q2[2] - q1[3]*q2[3]; float x = q1[0]*q2[1] + q1[1]*q2[0] + q1[2]*q2[3] - q1[3]*q2[2]; float y = q1[0]*q2[2] - q1[1]*q2[3] + q1[2]*q2[0] + q1[3]*q2[1]; float z = q1[0]*q2[3] + q1[1]*q2[2] - q1[2]*q2[1] + q1[3]*q2[0]; resultRef[0] = w; resultRef[1] = x; resultRef[2] = y; resultRef[3] = z; } Here is my code for applying a quaternion to my modelview matrix (I have a tmodelview variable that is my target modelview matrix): void cube::applyquat(){ float& x = quaternion[1]; float& y = quaternion[2]; float& z = quaternion[3]; float& w = quaternion[0]; float magnitude = sqrtf(w * w + x * x + y * y + z * z); if(magnitude == 0){ x = 1; w = y = z = 0; }else if(magnitude != 1){ x /= magnitude; y /= magnitude; z /= magnitude; w /= magnitude; } tmodelview[0] = 1 - (2 * y * y) - (2 * z * z); tmodelview[1] = 2 * x * y + 2 * w * z; tmodelview[2] = 2 * x * z - 2 * w * y; tmodelview[3] = 0; tmodelview[4] = 2 * x * y - 2 * w * z; tmodelview[5] = 1 - (2 * x * x) - (2 * z * z); tmodelview[6] = 2 * y * z - 2 * w * x; tmodelview[7] = 0; tmodelview[8] = 2 * x * z + 2 * w * y; tmodelview[9] = 2 * y * z + 2 * w * x; tmodelview[10] = 1 - (2 * x * x) - (2 * y * y); tmodelview[11] = 0; glMatrixMode(GL_MODELVIEW); glPushMatrix(); glLoadMatrixf(tmodelview); glMultMatrixf(modelview); glGetFloatv(GL_MODELVIEW_MATRIX, tmodelview); glPopMatrix(); } And my code for rotation (that I call externally), where quaternion is a class variable of the cube: void cube::rotatex(int angle){ float quat[4]; float ang = angle * PI / 180.0; quat[0] = cosf(ang / 2); quat[1] = sinf(ang/2); quat[2] = 0; quat[3] = 0; quatmul(quat, quaternion, quaternion); applyquat(); } void cube::rotatey(int angle){ float quat[4]; float ang = angle * PI / 180.0; quat[0] = cosf(ang / 2); quat[1] = 0; quat[2] = sinf(ang/2); quat[3] = 0; quatmul(quat, quaternion, quaternion); applyquat(); } void cube::rotatez(int angle){ float quat[4]; float ang = angle * PI / 180.0; quat[0] = cosf(ang / 2); quat[1] = 0; quat[2] = 0; quat[3] = sinf(ang/2); quatmul(quat, quaternion, quaternion); applyquat(); } I call, say rotatex, for 10-11 times for rotating only 1 degree, but my cube gets rotated almost 90 degrees after 10-11 times of 1 degree, which doesn't make sense. Also, after calling rotation functions in different axes, My cube gets skewed, gets 2 dimensional, and disappears (a column in modelview matrix becomes all zeros) irreversibly, which obviously shouldn't be happening with a correct implementation of the quaternions.

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  • Matrix Comparison algorithm

    - by SysAdmin
    If you have 2 Matrices of dimensions N*M. what is the best way to get the difference Rect? Example: 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 4 5 4 3 2 3 <---> 2 3 2 3 2 3 2 3 2 3 4 5 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 | | \ / Rect([2,2] , [3,4]) 4 5 4 4 5 2-> A (2 x 3 Matrix) The best I could think of is to scan from Top-Left hit the point where there is difference. Then scan from Bottom Right and hit the point where there is a difference. But In worst case, this is O(N*M). is there a better efficient algorithm?

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  • Reportviewer - Print report - matrix report expanding horizontally to multiple pages, avoid repeating row header

    - by abc0077
    I am generating a matrix report dynamically using report viewer version 9.0 in visual studio 2010. If i export save and print then it works normally. If there more columns report expands horizontally across mutiple pages. If i give Print option available in the toolbar of the report viewer. The columns are moved to second page which is correct but the row headers (product 1, product 2) should not be repeated in the second page.In the second page report should have all details except the product information. I am also interested to know whether it is the functionality of this version report viewer.

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  • Finding matching submatrics inside a matrix

    - by DaveO
    I have a 100x200 2D array expressed as a numpy array consisting of black (0) and white (255) cells. It is a bitmap file. I then have 2D shapes (it's easiest to think of them as letters) that are also 2D black and white cells. I know I can naively iterate through the matrix but this is going to be a 'hot' portion of my code so speed is an concern. Is there a fast way to perform this in numpy/scipy? I looked briefly at Scipy's correlate function. I am not interested in 'fuzzy matches', only exact matches. I also looked at some academic papers but they are above my head.

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  • Last Observation Carried Forward In a data frame?

    - by Tal Galili
    Hi all, I wish to implement a "Last Observation Carried Forward" for a data set I am working on which has missing values at the end of it. Here is a simple code to do it (question after it): LOCF <- function(x) { # Last Observation Carried Forward (for a left to right series) LOCF <- max(which(!is.na(x))) # the location of the Last Observation to Carry Forward x[LOCF:length(x)] <- x[LOCF] return(x) } # example: LOCF(c(1,2,3,4,NA,NA)) LOCF(c(1,NA,3,4,NA,NA)) Now this works great for simple vectors. But if I where to try and use it on a data frame: a <- data.frame(rep("a",4), 1:4,1:4, c(1,NA,NA,NA)) a t(apply(a, 1, LOCF)) # will make a mess It will turn my data frame into a character matrix. Can you think of a way to do LOCF on a data.frame, without turning it into a matrix? (I could use loops and such to correct the mess, but would love for a more elegant solution) Cheers, Tal

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  • How to access a matrix in a matlab struct's field from a mex function?

    - by B. Ruschill
    I'm trying to figure out how to access a matrix that is stored in a field in a matlab structure from a mex function. That's awfully long winded... Let me explain: I have a matlab struct that was defined like the following: matrixStruct = struct('matrix', {4, 4, 4; 5, 5, 5; 6, 6 ,6}) I have a mex function in which I would like to be able to receive a pointer to the first element in the matrix (matrix[0][0], in c terms), but I've been unable to figure out how to do that. I have tried the following: /* Pointer to the first element in the matrix (supposedly)... */ double *ptr = mxGetPr(mxGetField(prhs[0], 0, "matrix"); /* Incrementing the pointer to access all values in the matrix */ for(i = 0; i < 3; i++){ printf("%f\n", *(ptr + (i * 3))); printf("%f\n", *(ptr + 1 + (i * 3))); printf("%f\n", *(ptr + 2 + (i * 3))); } What this ends up printing is the following: 4.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 I have also tried variations of the following, thinking that perhaps it was something wonky with nested function calls, but to no avail: /* Pointer to the first location of the mxArray */ mxArray *fieldValuePtr = mxGetField(prhs[0], 0, "matrix"); /* Get the double pointer to the first location in the matrix */ double *ptr = mxGetPr(fieldValuePtr); /* Same for loop code here as written above */ Does anyone have an idea as to how I can achieve what I'm trying to, or what I am potentially doing wrong? Thanks! Edit: As per yuk's comment, I tried doing similar operations on a struct that has a field called array which is a one-dimensional array of doubles. The struct containing the array is defined as follows: arrayStruct = struct('array', {4.44, 5.55, 6.66}) I tried the following on the arrayStruct from within the mex function: mptr = mxGetPr(mxGetField(prhs[0], 0, "array")); printf("%f\n", *(mptr)); printf("%f\n", *(mptr + 1)); printf("%f\n", *(mptr + 2)); ...but the output followed what was printed earlier: 4.440000 0.000000 0.000000

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  • O'Reilly book clarification on 2d linear system

    - by Eric
    The Oreilly book "Learning openCV" states at page 356 : Quote Before we get totally lost, let’s consider a particular realistic situation of taking measurements on a car driving in a parking lot. We might imagine that the state of the car could be summarized by two position variables, x and y, and two velocities, vx and vy. These four variables would be the elements of the state vector xk. Th is suggests that the correct form for F is: x = [ x; y; vx; vy; ]k F = [ 1, 0, dt, 0; 0, 1, 0, dt; 0, 0, 1, 0; 0, 0, 0, 1; ] It seems natural to put 'dt' just there in the F matrix but I just don't get why. What if I have a n states system, how would I spray some "dt" in the F matrix?

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  • Multiplying Block Matrices in Numpy

    - by Ada Xu
    Hi Everyone I am python newbie I have to implement lasso L1 regression for a class assignment. This involves solving a quadratic equation involving block matrices. minimize x^t * H * x + f^t * x where x 0 Where H is a 2 X 2 block matrix with each element being a k dimensional matrix and x and f being a 2 X 1 vectors each element being a k dimension vector. I was thinking of using nd arrays. such that np.shape(H) = (2, 2, k, k) np.shape(x) = (2, k) But I figured out that np.dot(X, H) doesn't work here. Is there an easy way to solve this problem? Thanks in advance.

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  • JAVA. Writing a matrix in a file using column information.

    - by Dmitry
    Hello, everybody! I have a file in which a matrix is stored. This file has a RandomAccessFile type. This matrix is stored by columns. I mean that in an i-th row of this matrix an i-th column (of a real matrix) is stored. There is an example: i-th row: 1 2 3 4 (in the file). That means that the real matrix has an i-th column: (1 2 3 4)(transpose). I need to save this matrix in natural way (by rows) in a new file, which I will then open with FileReader and display with TestArea. DO you know, how to do that? If so, please help =)

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  • Reading Matrices in MATLAB and assigning coordinates to the entries

    - by Michael Schofield
    Hi, I'm a bit new to MATLAB. Basically, I have a 25x25 Matrix, complete with various random entries ranging from 0 to 3. I need to write a program that reads this matrix, and assigns x-y coordinates to the entries, so that when I ask for an input of a particular x-y coordinate which has, say an entry of 3, then it will result in an error. I'm a bit overwhelmed - but I understand the general concept of what I'm supposed to be finding. I'm wondering if I should use a plot instead to help me.

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