how to resolve this error "Index exceeds matrix dimensions."

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Shah Bano 2019-3-23

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https://ww2.mathworks.cn/matlabcentral/answers/451912-how-to-resolve-this-error-index-exceeds-matrix-dimensions

评论： Walter Roberson 2019-3-24

I am implementing HOG and while computing the cell histograms the code give me this error. Here is the code.

% =================================
%     Compute Cell Histograms 
% =================================
% Computes the histogram for every cell in the image. We'll combine the cells
H = [];
% Create a three dimensional matrix to hold the histogram for each cell.
histograms = zeros(hogParameters.numVertCells, hogParameters.numHorizCells, hogParameters.numBins);
% For each cell in the y-direction...
for row = 0:(hogParameters.numVertCells - 1)
    
    % Compute the row number in the 'img' matrix corresponding to the top
    % of the cells in this row. Add 1 since the matrices are indexed from 1.
    rowOffset = (row * hogParameters.cellSize) + 1;
    
    % For each cell in the x-direction...
    for col = 0:(hogParameters.numHorizCells - 1)
    
        % Select the pixels for this cell.
        
        % Compute column number in the 'img' matrix corresponding to the left
        % of the current cell. Add 1 since the matrices are indexed from 1.
        colOffset = (col * hogParameters.cellSize) + 1;
        
        % Compute the indices of the pixels within this cell.
        rowIndeces = rowOffset : (rowOffset + hogParameters.cellSize - 1);
        colIndeces = colOffset : (colOffset + hogParameters.cellSize - 1);
        
        % Select the angles and magnitudes for the pixels in this cell.
        cellAngles = angles(rowIndeces, colIndeces);    --> error line
        cellMagnitudes = magnitude(rowIndeces, colIndeces);     --> error line
    
        % Compute the histogram for this cell.
        % Convert the cells to column vectors before passing them in.
        histograms(row + 1, col + 1, :) = getHistogram(cellMagnitudes(:), cellAngles(:), hogParameters.numBins);
    end

At the cellAngles and cellMagnitude it shows error. Kinldy someone resolve this error.

I shall be very thankful for the kind act of consideration.

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Shah Bano 2019-3-23

编辑：Walter Roberson 2019-3-24

在 MATLAB Online 中打开

These are the hog parameters

treshold = 10;
hogParameters.numBins = 9;%number of bins
hogParameters.numHorizCells = 8;%number of cells in x direction
hogParameters.numVertCells = 16;%number of cells in y direction
hogParameters.cellSize = 8; %pixel number in image
hogParameters.winSize = [(hogParameters.numVertCells * hogParameters.cellSize + 2),(hogParameters.numHorizCells * hogParameters.cellSize + 2)];% Expected window size.
objectImage = rgb2gray(load_images{k});
% Compute Gradient
% Create the operators for computing image derivative at every pixel.
hx = [-1,0,1];
hy = hx';
% Compute the derivative in the x and y direction for every pixel.
dx = filter2(hx, double(objectImage));
dy = filter2(hy, double(objectImage));
% Remove the 1 pixel border.
dx = dx(2 : (size(dx, 1) - 1), 2 : (size(dx, 2) - 1));
dy = dy(2 : (size(dy, 1) - 1), 2 : (size(dy, 2) - 1)); 
% Convert the gradient vectors to polar coordinates (angle and magnitude).
angles = atan2(dy, dx);
magnitude = ((dy.^2) + (dx.^2)).^.5;

Walter Roberson 2019-3-24

编辑：Walter Roberson 2019-3-24

This code appears to rely on functions from https://github.com/buzkent86/HLT_Tracker/blob/master/getHistogram.m

Walter Roberson 2019-3-24

hogpen.m

When I test with a random image, I am not encountering any problem. I have attached my test code.

The problem might depend upon the image you are using. You should dbstop if error and find out which image is causing you problems, and attach that image.

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