# Plot a heatmap from a matix

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Ahmed Madhun on 25 Oct 2019
Edited: Ahmed Madhun on 26 Oct 2019
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 on 26 Oct 2019
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 on 26 Oct 2019
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 on 26 Oct 2019
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.

darova on 26 Oct 2019
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

Show 8 older comments
Ahmed Madhun on 26 Oct 2019
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 on 26 Oct 2019
Can you attach a screenshot or something? The file is too large, can't donwload .pdf (i have low internet speed)
Ahmed Madhun on 26 Oct 2019
The paper is only 8 Mb. You can find it if you search on google for: "Learning a Fixed-Length Fingerprint Representation"