Visualize Sparsity Pattern of A Matrix by MATLAB spy Function
Jul. 11, 2025 • Updated Jul. 11, 2025
MATLAB spy function is to “visualize sparsity pattern of matrix”1, for example:
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clc, clear, close all
[B, ~] = bucky;
spy(B, 'r.', 10)
exportgraphics(gca, "fig.jpg", "Resolution", 600)
where the bucky function is to generate a bucky ball adjacency matrix, which is a 60-by-60 symmetric sparse matrix with only 180 nonzero elements (the density of this matrix is 5%)2.
Alternatively, I think maybe we can use another function, imagesc, to realize a similar effect (refer to3):
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clc, clear, close all
[B, ~] = bucky;
imagesc(B)
% colorbar
exportgraphics(gca, "fig.jpg", "Resolution", 600)
Besides, format + is another way, a text-based alternative, to display the nonzero structure of a matrix1:
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clc, clear, close all
[B, ~] = bucky;
B = full(B);
format +
B
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References