How to speed up iterating a large data in a nested loop ?
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%example
a=1x1000;
b=1x1000;
for i=1:length(a)
for j 1:length(b)
x(i,j)=cos(a(i));
y(i,j)=sin(b(j));
end
end
Thank you and appreciate!
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Réponses (1)
Image Analyst
le 5 Déc 2020
Try this:
% Create sample data.
% numPoints = 500;
a = pi * rand(1, numPoints);
b = pi * rand(1, numPoints);
% Create x and y
x = repmat(cos(a(:)), [1, numPoints]);
y = repmat(sin(b), [numPoints, 1]);
% Display the x and y matrices:
cmap = jet(256);
subplot(2, 1, 1);
imshow(x, [], 'Colormap', cmap);
colorbar;
title('x', 'FontSize', 20);
subplot(2, 1, 2);
imshow(y, [], 'Colormap', cmap);
colorbar;
title('y', 'FontSize', 20);
2 commentaires
Image Analyst
le 6 Déc 2020
If things depend on only k, and not j, then put them between the k and j loop, not inside the j loop.
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