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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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• 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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• 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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• 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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• 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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• 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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• 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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• Looking for PCA snippet/source code in C++

  - by jihchuan

  Hi, I'm currently developing a software to compare 2 images. I start with extract the image's RGB values, form a matrix of array and then attempt to compress the values using PCA, and then match/recognize it with a pre-set data to find its similarity. But I can't proceed with the PCA part. (I'm using C++, C also can) If there any library/source code/snippet for it please let me know, or if there're any recommendation on my case also very welcomed!! I'd appreciate your helps!! Thanks! JC, [email protected]

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• Out of memory error while using clusterdata in MATLAB

  - by Hossein

  Hi, I am trying to cluster a Matrix (size: 20057x2).: T = clusterdata(X,cutoff); but I get this error: ??? Error using == pdistmex Out of memory. Type HELP MEMORY for your options. Error in == pdist at 211 Y = pdistmex(X',dist,additionalArg); Error in == linkage at 139 Z = linkagemex(Y,method,pdistArg); Error in == clusterdata at 88 Z = linkage(X,linkageargs{1},pdistargs); Error in == kmeansTest at 2 T = clusterdata(X,1); can someone help me. I have 4GB of ram, but think that the problem is from somewhere else..

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• vectorization of a text file

  - by Fox

  I am trying to implement vectorization of a text file...I have created a dictionary (Unique words in all the documents) ... Which is the best way to implement this in java? For example - My dictionary has the following words - {w1, w2, w3, w4} And I have 2 documents each having subset of the words in the vocabulary. I need to write to a text file the matrix in the form -- 1,3,4,0 0,0,2,1 Here each row represents a document and the values represent the occurrence of each word in the document. Can you suggest me the most efficient way to implement this in Java?

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• Entity Framework use of indexes and foreign keys

  - by David

  I want to be able to search a table quite quickly using the Entity Framework, say if I have a Contacts table, a JobsToDo table and a matrix table linking the two tables e.g Contacts_JobsToDo_Mtx and I specify two foreign keys in the Contacts_JobsToDo_Mtx table, if I wanted to search this Mtx table, do I need to specify an index on the two foreign keys? Or by the fact that they are two foreign keys are they considered indexed on them anyway? Will the Entity Framework be able to search through the Mtx table quickly without having to specfiy an index on both keys? Thanks!

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• iPhone status bar orientation with opengl

  - by sfider

  I have opengl only view that displays in portrait and landscape mode using projection matrix (view's transformation is identity all the time). I need to show status bar with proper orientation. I do this by setting status bar orientation property in UIApplication and changing frame of opengl view so the view won't go under status bar. When I change from landscape to portrait (landscape is the initial state) view's frame is set to (0, 20, 320, 460) and stays like this. However view appears to be translated by (-10, -10). It seems that I did change the size of view but couldn't move it. Weird things are: initialy view is full screen, I change it to (0, 0, 300, 480) (landscape with status bar) and it works then, it doesn't work when I try to chenge it for the second time (portrait with status bar) frame property of the view shows that view is placed correctly Any thoughts on what can by the problem?

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• How to optimize MATLAB loops?

  - by striglia

  I have been working lately on a number of iterative algorithms in MATLAB, and been getting hit hard by MATLAB's performance (or lack thereof) when it comes to loops. I'm aware of the benefit of vectorizing code when possible, but are there any tools for optimization when you need the loop for your algorithm? I am aware of the MEX-file option to write small subroutines in C/C++, although given my algorithms, this can be a very painful option given the data structures required. I mainly use MATLAB for the simplicity and speed of prototyping, so a syntactically complex, statically typed language is not ideal for my situation. Are there any other suggestions? Even other languages (python?) which have relatively painless matrix tools are an option.

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• NSString stringWithFormat: with C array?

  - by Chris Long

  Hi, I'm writing a program that calculates the Jacobi algorithm. It's written in Objective-C since it runs on a Mac, but the majority is written in standard C. I'm using a two-dimensional C array and an NSArray containing 5 NSTextField labels. The following code yields an EXC_BAD_ACCESS error: for ( int i = 0; i < 5; i++ ) { NSString *resultString = [NSString stringWithFormat:@"%g", matrix[i][i] ]; [[resultLabels objectAtIndex:i] setStringValue:resultString]; // error line } Any help?

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• Changing text size on a ggplot bump plot

  - by Tom Liptrot

  Hi, I'm fairly new to ggplot. I have made a bumpplot using code posted below. I got the code from someones blog - i've lost the link.... I want to be able to increase the size of the lables (here letters which care very small on the left and right of the plot) without affecting the width of the lines (this will only really make sense after you have run the code) I have tried changing the size paramater but that always alter the line width as well. Any suggestion appreciated. Tom require(ggplot2) df<-matrix(rnorm(520), 5, 10) #makes a random example colnames(df) <- letters[1:10] Price.Rank<-t(apply(df, 1, rank)) dfm<-melt(Price.Rank) names(dfm)<-c( "Date","Brand", "value") p <- ggplot(dfm, aes(factor(Date), value, group = Brand, colour = Brand, label = Brand)) p1 <- p + geom_line(aes(size=2.2, alpha=0.7)) + geom_text(data = subset(dfm, Date == 1), aes(x = Date , size =2.2, hjust = 1, vjust=0)) + geom_text(data = subset(dfm, Date == 5), aes(x = Date , size =2.2, hjust = 0, vjust=0))+ theme_bw() + opts(legend.position = "none", panel.border = theme_blank()) p1 + theme_bw() + opts(legend.position = "none", panel.border = theme_blank())

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• Comparing images using SIFT

  - by Luís Fernando

  I'm trying to compare 2 images that are taken from a digital camera. Since there may be movement on the camera, I want to first make the pictures "match" and then compare (using some distant function). To match them, I'm thinking about cropping the second picture and using SIFT to find it inside the first picture... it will probably have a small difference on scale/translation/rotation so then I'd need to find the transformation matrix that converts image 1 to image 2 (based on points found by SIFT) any ideas on how to do that (or I guess that's a common problem that may have some opensource implementation?)? thanks

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• count of distinct acyclic paths from A[a,b] to A[c,d]?

  - by Sorush Rabiee

  I'm writing a sokoban solver for fun and practice, it uses a simple algorithm (something like BFS with a bit of difference). now i want to estimate its running time ( O and omega). but need to know how to calculate count of acyclic paths from a vertex to another in a network. actually I want an expression that calculates count of valid paths, between two vertices of a m*n matrix of vertices. a valid path: visits each vertex 0 or one times. have no circuits for example this is a valid path: but this is not: What is needed is a method to find count of all acyclic paths between the two vertices a and b. comments on solving methods and tricks are welcomed.

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• Matlab: Adding symbols to figure

  - by niko

  Hi, Below is the user interface I have created to simulate LDPC coding and decoding The code sequence is decoded iteratively by passing values between the left and right nodes through the connections. The first thing it would be good to add in order to improve visualization is to add arrows to the connections in the direction of passing values. The alternative is to draw a bigger arrow at the top of the connection showing the direction. Another thing I would like to do is displaying the current mathematical operation below the connection (in this example c * H'). What I don't know how to do is displaying special characters and mathematical symbols and other kinds of text such as subscript and superscript in the figure (for example sum sign and subscript "T" instead of sign ="'" to indicate transposed matrix). I would be very thankful if anyone could point to any useful resources for the questions above or show the solution. Thank you.

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• Maths: Determining angle in 3D space

  - by 742

  I hope this is the proper location to ask this question which is the same as this one, but expressed as pure math instead of graphically (at least I hope I translated the problem to math correctly). Considering: two vectors that are orthogonal: Up (ux, uy, uz) and Look (lx, ly, lz) a plane P which is perpendicular to Look (hence including Up) Y1 which is the projection of Y (vertical axis) along Look onto P Question: what is the value of the angle between Y1 and Up? As mathematicians will agree, this is a very basic question, but I've been scratching my head on walls now for at least two weeks without being able to visualize the solution... maybe now too old for finding solutions to school exercises. I'm looking for the scalar trigonometric solution, not a solution using a matrix. Thanks.

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