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• OpenCV: How to copy CvSeq data into CvMat?

  - by Can Bal

  I have a CvSeq structure at hand, which is the output of an available OpenCV function. This holds 128 bytes of data in each of the sequence elements. I want to copy each of these 128-byte elements into rows of a CvMat structure to form a N-by-128 of type CV_32FC1. What would be the most efficient way to do this? I thought of using memcpy but I couldn't come up with a working solution. For the details, I want to calculate the SURF features in an image by cvExtractSURF() function, and copy the SURF descriptors into a matrix for passing it to the cvKMeans2().

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• Noise Estimation / Noise Measurement in Image

  - by Drazick

  Hello. I want to estimate the noise in an image. Let's assume the model of an Image + White Noise. Now I want to estimate the Noise Variance. My method is to calculate the Local Variance (3*3 up to 21*21 Blocks) of the image and then find areas where the Local Variance is fairly constant (By calculating the Local Variance of the Local Variance Matrix). I assume those areas are "Flat" hence the Variance is almost "Pure" noise. Yet I don't get constant results. Is there a better way? Thanks.

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• NDepend query methods/types in framework assembly being used by other assemblies/types

  - by icelava

  I am trying to determine which types or methods in a base framework assembly are being used by other assemblies in the application system. I cannot seem to find a straight-cut query to do that. What i have to do is first determine which assemblies are directly using the framework assembly, then manually list them in a second query SELECT TYPES FROM ASSEMBLIES "IBM.Data.DB2" WHERE IsDirectlyUsedBy "ASSEMBLY:FirstDirectUsedByAssebmly" OR IsDirectlyUsedBy "ASSEMBLY:SecondDirectUsedByAssebmly" OR IsDirectlyUsedBy "ASSEMBLY:ThirdDirectUsedByAssebmly" OR IsDirectlyUsedBy "ASSEMBLY:FourthDirectUsedByAssebmly" Is there a better/faster way to query for this? Additionally, the query results are focused on the matched types only. The Dependency graph or matrix exported only shows details of those. I do not know how to render a graph that shows those types or methods plus show the dependent types/methods from other assemblies that are consuming them?

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• Calculating determinant by hand

  - by ldigas

  Okey, this is only half programming, but let's see how you are on terms with manual calculations. I believe many of you did this on your university's while giving "linear systems" ... the problem is it's been so long I can't remember how to do it any more. I know quite a few algorithms for calculating determinants, and they all work fine ... for large systems, where one would never try to do it manually. Unfortunatelly, I'm soon going on an exam, where I do have to calculate it manually, up to the system of 5. So, I have a K(omega) matrix that looks like this: [2-(omega^2)*c -4 2 0 0] [-2 5-(omega^2)*c -4 1 0] [1 -4 6-(omega^2)*c -4 1] [0 1 -4 5-(omega^2)*c -2] [0 0 2 -4 2-(omega^2)*c] and I need all the omegas which satisfy the det[K(omega)]=0 criteria. What would be a good way to calculate it so it can be repeated in a manual process ?

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• OpenCL or OpenGL – which one to use?

  - by Malte Schledjewski

  My Problem involves a black and white image with a black area in the middle. I never worked with OpenGL or OpenCL before so I do not know which one to chose. I want to put some white circles over the area and check at the end whether the whole image is white. I will try many combinations so I want to use the GPU because of its parallelism. Should I use OpenGL and create the circle as a texture and put it on top of the image or should I write some OpenCL kernels which work on the pixel/entries in the matrix?

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• java cosine similarity problem

  - by agazerboy

  Hi again :) I developed some java program to calculate cosine similarity on the basis of TF*IDF. It worked very well. But there is one problem.... :( for example: If I have following two matrix and I want to calculate cosine similarity it does not work as rows are not same in length doc 1 1 2 3 4 5 6 doc 2 1 2 3 4 5 6 7 8 5 2 4 9 if rows and colums are same in length then my program works very well but it does not if rows and columns are not in same length. Any tips ???

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• Replace empty cells with logical 0's before cell2mat in MATLAB

  - by Doresoom

  I've got a cell array of empty cells and ones that I want to convert to a logical array, where the empty cells are zeros. When I use cell2mat, the empty cells are ignored, and I end up with a matrix of solely 1's, with no reference to the previous index they held. Is there a way to perform this operation without using loops? Example code: for n=1:5 %generate sample cell array mycellarray{n}=1; end mycellarray{2}=[] %remove one value for testing Things I've tried: mylogicalarray=logical(cell2mat(mycellarray)); which results in [1,1,1,1], not [1,0,1,1,1]. for n=1:length(mycellarray) if isempty(mycellarray{n}) mycellarray{n}=0; end end mylogicalarray=logical(cell2mat(mycellarray)); which works, but uses loops.

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• delete pointer to 2d array c ++

  - by user1848054

  i have this pointer to 2d array of Robot class Robot ***rob; and this is here the code for the constructor !! and the program works fine !!! but now i am trying to build a destructor to delete this pointer !! and it keeps on crashing the program !! my question is , how to delete this pointer to 2d array of robots ? RobotsWorld::RobotsWorld(int x , int y) { X=x;Y=y; // returns the limitation of the matrix rob = new Robot**[x]; for(int i = 0; i < x; i++) { rob[i] = new Robot*[y]; for(int j = 0; j < y; j++) { rob[i][j] = NULL; } } }

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• Typecast to an int in Octave/Matlab

  - by Leif Andersen

  I need to call the index of a matrix made using the linspace command, and based on somde data taken from an oscilloscope. Because of this, the data inputed is a double. However, I can't really call: Time[V0Found] where V0Found is something like 5.2 however, taking index 5 is close enough, so I need to drop the decimal. I used this equation to drop the decimal: V0FoundDec = V0Found - mod(V0Found,1) Time[V0FoundDec] However, eve though that drops the decimal, octave still complains about it. So, what can I do to typecast it to an int? Thank you.

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• Implementing PageRank using MapReduce

  - by Nick D.

  Hello, I'm trying to get my head around an issue with the theory of implementing the PageRank with MapReduce. I have the following simple scenario with three nodes: A B C. The adjacency matrix is here: A { B, C } B { A } The PageRank for B for example is equal to: (1-d)/N + d ( PR(A) / C(A) ) N = number of incoming links to B PR(A) = PageRank of incoming link A C(A) = number of outgoing links from page A I am fine with all the schematics and how the mapper and reducer would work but I cannot get my head around how at the time of calculation by the reducer, C(A) would be known. How will the reducer, when calculating the PageRank of B by aggregating the incoming links to B will know the number of outgoing links from each page. Does this require a lookup in some external data source?

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• Daubechies-4 Transform in MATLAB

  - by Myx

  Hello: I have a 4x4 matrix which I wish to decompose into 4 frequency bands (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4 wavelet transform. As a result of the transform, each band should contain 2x2 coefficients. How can I do this in MATLAB? I know that MATLAB has dbaux and dbwavf functions. However, I'm not sure how to use them and I also don't have the wavelet toolbox. Any help is greatly appreciated. Thanks.

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• A definitive guide to Url Encoding in ASP .NET

  - by cbp

  I am starting to realise that there are about a bazillion different methods for encoding urls in .NET. I keep finding new ones. They all work slightly differently, but they all have essentially the same summary comments. Does anyone have a definitive matrix that shows the exact differences between the following methods: HttpUtility.UrlEncode HttpUtility.UrlPathEncode Server.UrlEncode Uri.EscapeUriString Uri.EscapeDataString ... are they any more? Also it would be good to match these up with use-cases e.g.: Urls in href attributes of a tags Urls to be displayed to the user in HTML Urls as querystring values (i.e. to be sent in GET requests) Urls to be sent in POST requests etc

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• Metric 3d reconstruction

  - by srand

  I'm trying to reconstruct 3D points from 2D image correspondences. My camera is calibrated. The test images are of a checkered cube and correspondences are hand picked. Radial distortion is removed. After triangulation the construction seems to be wrong however. The X and Y values seem to be correct, but the Z values are about the same and do not differentiate along the cube. The 3D points look like as if the points were flattened along the Z-axis. What is going wrong in the Z values? Do the points need to be normalized or changed from image coordinates at any point, say before the fundamental matrix is computed? (If this is too vague I can explain my general process or elaborate on parts)

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• how to build an accumulator array in matlab

  - by schwiz

  I'm very new to matlab so sorry if this is a dumb question. I have to following matrices: im = imread('image.jpg'); %<370x366 double> [y,x] = find(im); %x & y both <1280x1 double> theta; %<370x366 double> computed from gradient of image I can currently plot points one at a time like this: plot(x(502) + 120*cos(theta(y(502),x(502))),y(502) + 120*sin(theta(y(502),x(502))),'*b'); But what I want to do is some how increment an accumulator array, something like this: acc = zeros(size(im)); acc(y,x) = acc(x + 120*cos(theta(y,x)),y + 120*sin(theta(y,x)),'*b')) + 1; It would be nice if the 120 could actually be another matrix containing different radius values as well.

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• java jama array problem

  - by agazerboy

  Hi All, I asked a question before but duffymo said it is not clear so i am going to post it again here. I am using Jama api for SVD calculation. I know very well about jama and SVD. Jama does not work if your column are more than rows. I have this situation. What should I do?? any help? I can't transpose the matrix too as it can produce wrong results. Thanks. P.S: I am calculating LSI with the help of jama. I am going like column(docs) and rows ( terms )

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• R heatmaps - non-text labels?

  - by Carl

  I am making a heatmap plot; currently the axes are labeled by index number. However, the index number corresponds to a series of 1/0s, which my group typically represents with a row of filled(1) or unfilled(0) boxes (think chessboard, though not strictly alternating colors). I'd like to use that representation instead of the index numbers. Any suggestions? I've considered simply making the labels as a plot, and positioning that adjacent to the heatmap, but I'm not finding a convenient way to do that either. I will also appreciate answers that are more generically applicable. edit - current code: map <- data.matrix(read.csv("./heatmap.out", header=F, sep=" ")) # ...some clean-up p<-heatmap(map, Rowv=NA, Colv=NA, col=grey(10:0 / 10)) this simply labels the heatmap rows/cols by index number. heatmap.out is raw numeric data.

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• Are stack based arrays possible in C#?

  - by Bob

  Let's say, hypothetically (read: I don't think I actually need this, but I am curious as the idea popped into my head), one wanted an array of memory set aside locally on the stack, not on the heap. For instance, something like this: private void someFunction() { int[20] stackArray; //C style; I know the size and it's set in stone } I'm guessing the answer is no. All I've been able to find is heap based arrays. If someone were to need this, would there be any workarounds? Is there any way to set aside a certain amount of sequential memory in a "value type" way? Or are structs with named parameters the only way (like the way the Matrix struct in XNA has 16 named parameters (M11-M44))?

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• Sudoku solver evaluation function

  - by Rich

  Hi, So I'm trying to write a simple genetic algorithm for solving a sudoku (not the most efficient way, I know, but it's just to practice evolutionary algorithms). I'm having some problems coming up with an efficient evaluation function to test if the puzzle is solved or not and how many errors there are. My first instinct would be to check if each row and column of the matrix (doing it in octave, which is similar to matlab) have unique elements by ordering them, checking for duplicates and then putting them back the way they were, which seems long winded. Any thoughts? Sorry if this has been asked before...

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• store/load numpy array from binary files

  - by Javier

  Dear all, I would like to store and load numpy arrays from binary files. For that purposes, I created two small functions. Each binary file should contain the dimensionality of the given matrix. def saveArrayToFile(data, fileName): with open(fileName, 'w') as file: a = array.array('f') nSamples, ndim = data.shape a.extend([nSamples, ndim]) # write number of elements and dimensions a.fromstring(data.tostring()) a.tofile(file) def readArrayFromFile(fileName): _featDesc = np.fromfile(fileName, 'f') _ndesc = int(_featDesc[0]) _ndim = int(_featDesc[1]) _featDesc = _featDesc[2:] _featDesc = _featDesc.reshape([_ndesc, _ndim]) return _featDesc, _ndesc, _ndim An example on how to use the functions is: myarr=np.array([[7, 4],[3, 9],[1, 3]]) saveArrayToFile(myarr,'myfile.txt') _featDesc, _ndesc, _ndim = readArrayFromFile('myfile.txt') However, an error message of 'ValueError: total size of new array must be unchanged' is shown. My arrays can be of size MxN and MxM. Any suggestions are more than welcomed. I think the problem might be in the saveArrayToFile function. Best wishes, Javier

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• Continuous Integration or Publishing System

  - by Chris M

  I've been testing Hudson for a few days now and for PHP projects it seems ok; What I need though is a system that will allow me to publish an SVN tag to an FTP folder without adding a pile of rubbish on the end; hudson gets overexcited and adds a pile of folders to the export. Are their any other decent systems; it needs to be simple to use as this will eventually fall under the control of 'admins' in order to meet sox compliance (aka the man with the gun cant pull the trigger). Basic Requirements: Must be free and downloadable to a server (FTP's internal only here) Needs to be able to interact with SVN Needs to be able to publish to FTP Needs matrix login permissions (or AD if its something that can go on IIS) Needs to be auditable (logging) Tell me if im not being clear enough here; thanks. Chris

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• cmake, gcc, cuda and -m32 wtf

  - by Nils

  Hi all I figured out that CUDA does not work in 64bit mode on my mac (or couldn't get it running so far). Therefore I decided to compile everything for 32bit. I use cmake 2.8 and added the following options add_definitions(-Wall -m32) set(CUDA_64_BIT_DEVICE_CODE OFF) set(CMAKE_MODULE_LINKER_FLAGS -m32) However when it tries to link it it does something like this: /usr/bin/c++ -mmacosx-version-min=10.6 -Wl,-search_paths_first -headerpad_max_install_names CMakeFiles/SimpleTestsCUDA.dir/BlockMatrix.cpp.o CMakeFiles/SimpleTestsCUDA.dir/Matrix.cpp.o ./SimpleTestsCUDA_generated_SimpleTests.cu.o ./SimpleTestsCUDA_generated_BlockMatrix.cu.o -o SimpleTestsCUDA /usr/local/cuda/lib/libcudart.dylib /usr/local/cuda/lib/libcuda.dylib Which fails with a lot of "file is not of required architecture" warnings from ld. Now if I add manually -m32 to the command above it works. However I have no idea how to teach cmake to add -m32 to every gcc (or ld) invocation. So far it does it for nvcc and gcc, but not for linking..

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• width of a frustum at a given distance from the near plane

  - by structolite

  I'm using CML to manage the 3D math in an OpenGL-based interface project I'm making for work. I need to know the width of the viewing frustum at a given distance from the eye point, which is kept as a part of a 4x4 matrix that represents the camera. My goal is to position gui objects along the apparent edge of the viewport, but at some distance into the screen from the near clipping plane. CML has a function to extract the planes of the frustum, giving them back in Ax + By + Cz + D = 0 form. This frustum is perpendicular to the camera, which isn't necessarily aligned with the z axis of the perspective projection. I'd like to extract x and z coordinates so as to pin graphical elements to the sides of the screen at different distances from the camera. What is the best way to go about doing it? Thanks!

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• VC7.1 C1204 internal compiler error

  - by Nathan Ernst

  I'm working on modifying Firaxis' Civilization 4 core game DLL. The host application is built using VC7, hence the constraint (source not provided for the host EXE). I've been working on rewriting a large chunk of the code (focusing on low-hanging performance issues & memory leaks). I recently ran into an internal compiler error when trying to mod the code to use an array class instead of dynamically allocated 2-d arrays, I was going to use matrices from the boost lib (Civ4 is already using boost, so why not?). Basically, the issue comes down to: if I include "boost/numeric/ublas/matrix.hpp", I run into an internal compiler error C1204. MSDN has this to say: MSDN C1204 KB has this to say: KB 883655 So, I'm curious, is it possible to solve this error without a KB/SP being applied and dramatically reducing the complexity of the code? Additionally, as VC7 is no longer "supported", does anyone have a valid (supported) link for a VC7 service pack?

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• Converting python objects for rpy2

  - by bgbg

  The following code is supposed to created a heatmap in rpy2 import numpy as np from rpy2.robjects import r data = np.random.random((10,10)) r.heatmap(data) However, it results in the following error Traceback (most recent call last): File "z.py", line 8, in <module> labRow=rowNames, labCol=colNames) File "C:\Python25\lib\site-packages\rpy2\robjects\__init__.py", line 418, in __call__ new_args = [conversion.py2ri(a) for a in args] File "C:\Python25\lib\site-packages\rpy2\robjects\__init__.py", line 93, in default_py2ri raise(ValueError("Nothing can be done for the type %s at the moment." %(type(o)))) ValueError: Nothing can be done for the type <type 'numpy.ndarray'> at the moment. From the documentation I learn that r.heatmap expects "a numeric matrix". How do I convert np.array to the required data type?

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• unevenly centered subplots in matplotlib in Python?

  - by user248237

  I am plotting a simple pair of subplots in matplotlib that are for some reason unevenly centered. I plot them as follows: plt.figure() # first subplot s1 = plt.subplot(2, 1, 1) plt.bar([1, 2, 3], [4, 5, 6]) # second subplot s2 = plt.subplot(2, 1, 2) plt.pcolor(rand(5,5)) # add colorbar plt.colorbar() # square axes axes_square(s1) axes_square(s2) where axes_square is simply: def axes_square(plot_handle): plot_handle.axes.set_aspect(1/plot_handle.axes.get_data_ratio()) The plot I get is attached. The top and bottom plots are unevenly centered. I'd like their yaxis to be aligned and their boxes to be aligned. If I remove the plt.colorbar() call, the plots become centered. How can I have the plots centered while the colorbar of pcolor is still shown? I want the axes to be centered and have the colorbar be outside of that alignment, either to the left or to the right of the pcolor matrix. image of plots link thanks.

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