Plot a heatmap from a matix

Asked by Ahmed Madhun on 25 Oct 2019

Latest activity Edited by Ahmed Madhun on 26 Oct 2019

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I implemented the minutia heat map presented in this paper (page 7): https://arxiv.org/pdf/1909.09901.pdf

The result is that i have 6 matrixes and i am looking for a way to plot these as shown in the paper (same page), like this:

Basically, the low values is presented in dark, and it gets lighter when it increase.

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Ahmed Madhun 2019 年 10 月 26 日

Thanks it seems to work, however, it sees to not be accurate. Because all my 6 matrixes are different, but when i use:

heatmap(Mx, 'Colormap',gray,'GridVisible','off'));

all the figures are the same, any idea of why this happen ?

darova 2019 年 10 月 26 日

Make range for color axis the same for each figure

min = % minimum of 6 matrix
max = % maximum of 6 matrix
caxis([min max])

Ahmed Madhun 2019 年 10 月 26 日

Sorry didn't get you comment: how to apply that for my code ?

% Function to create the HeatMap matrix of a minutia set in "TestData" file
function HeatMapCreator()
    % Start plotting minutia 
    [X, Y, A] = GetMinData("TestData");
    % Minutia 1 has X1, Y1, and A1 => X and Y is the position and A is the angle between 0-359
    % Count Minutiea
    n = length(X);
    % set Width and Hight
    W = 600;
    H = 750;
    K = 6;
    
    % Create the matixes
    MM = cell(K, 1);
    M = zeros(H,W);
    
    % Define the gussian paramater
    GP = 2*2^2;
    
    % Go throw each pixel
    for k = 1:6
        for i = 1 : W
           for j = 1 : H
              Hijk = 0; 
              for t = 1 : n
                Xt = X(t);
                Yt = Y(t);
                At = A(t);
                %Calculate Cs
                ED = sqrt((i-Xt)^2+(j-Yt)^2);
                Cs = exp(-ED/GP);
                %Calculate Co
                DO = At - (2 * k * pi / K);
                if (DO < -pi) || (DO > pi)
                    DO = 2 * pi - DO;
                end                       
                Co = exp(-DO/GP);
                Hijk = Hijk + (Cs * Co);
              end
              M(i,j) = Hijk;
           end
        end
        MM{k} = M;
    end
    
    % Show the 6 figures
    for k = 1:6
        figure(k)
        heatmap(MM{k},'Colormap',gray,'GridVisible','off');
    end
end

Comment: I set the Gussian paramater to test weather it works or not.

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回答者: darova 2019 年 10 月 26 日

採用された回答

You are using H for rows and W for columns

M1 = zeros(H,W);
% ...
for i = 1 : W
    for j = 1 : H
        % ...
        M1(i,j) = Hijk;        % looks like mistake

You can use cells to create 6 matrices automatically

MM = cell(6,1);
M = zeros(H,W);
for k = 1:6
    for i 
        for j
            for t
                % do stuff
            end
            % ...
            M(i,j) = %...
        end
    end
    MM{k} = M;
end

After you found max and min values (global) use loop to visualize

for k = 1:6
    figure(k)
    heatmap(MM{k});
    caxis([minx maxx])
    colormap gray
end

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Ahmed Madhun 2019 年 10 月 26 日

Not really, no value is now displayed on the heatmap figures at all.

I change my code as you advised:

    minV = 0;
    maxV = 0;
    
    for k = 1:6
        for i = 1 : W
           for j = 1 : H
              Hijk = 0; 
              for t = 1 : n
                Xt = X(t);
                Yt = Y(t);
                At = A(t);
                %Calculate Cs
                ED = sqrt((i-Xt)^2+(j-Yt)^2);
                Cs = exp(-ED/GP);
                %Calculate Co
                DO = At - (2 * k * pi / K);
                if (DO < -pi) || (DO > pi)
                    DO = 2 * pi - DO;
                end                       
                Co = exp(-DO/GP);
                Hijk = Hijk + (Cs * Co);
              end
              M(i,j) = Hijk;
           end
        end
        MM{k} = M;
        
        % Get the maximum and minimum cell from all matrixes
        if minV > min(M(:))
            minV = min(M(:));
        end
        
        if maxV < max(M(:))
            maxV = max(M(:));
        end
    end
    
    for k = 1:6
        figure(k)
        heatmap(MM{k})
        caxis([minV maxV])
        colormap gray
    end

the result is:

However, if i use the old code to display the heatmap as:

heatmap(MM{1},'Colormap',gray,'GridVisible','off');

the result is:

But this is equal for all matrixes!, which is not correct as all matrixes are different!

Ahmed Madhun 2019 年 10 月 26 日

Not sure, because according to the paper. If it's implemented correctly each heat map should highlight only minutia in the same degree range.

darova 2019 年 10 月 26 日

Can you attach a screenshot or something? The file is too large, can't donwload .pdf (i have low internet speed)

Ahmed Madhun 2019 年 10 月 26 日

The paper is only 8 Mb. You can find it if you search on google for: "Learning a Fixed-Length Fingerprint Representation"

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