Contour Plot with Boolean Indices (z must be at least a 2x2 matrix)
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Robert Zukowski
2023 年 4 月 24 日
コメント済み: Robert Zukowski
2023 年 4 月 24 日
I'm trying to create a contour plot where the output depends on a condition from the input. An example is shown below.
The code is supposed to assign Z=Y when Y<=5 and Z=X when Y>5.
X = 1:1:5;
Y = 1:1:10;
[X,Y] = meshgrid(X, Y);
bool = Y <= 5;
Z(bool) = Y(bool);
Z(~bool) = X(~bool);
contour(X,Y,Z)
I know that the bool variable is getting initialized correctly, but for some reason, Z becomes a really long vector instead of keeping its dimensions. (which gives the error using contour: Z must be at least a 2x2 matrix)
I'm not sure how to approach this problem differently, so any insight is greatly appreciated.
Thanks!
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採用された回答
Walter Roberson
2023 年 4 月 24 日
X = 1:1:5;
Y = 1:1:10;
[X,Y] = meshgrid(X, Y);
Z = X;
bool = Y <= 5;
Z(bool) = Y(bool);
contour(X,Y,Z)
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その他の回答 (1 件)
LeoAiE
2023 年 4 月 24 日
The issue you're facing is due to the fact that when you use logical indexing with an uninitialized array like Z, MATLAB automatically converts it into a vector. To fix this issue, you can initialize the Z array with the same size as X and Y using the zeros function.
X = 1:1:5;
Y = 1:1:10;
[X,Y] = meshgrid(X, Y);
bool = Y <= 5;
Z = zeros(size(X));
Z(bool) = Y(bool);
Z(~bool) = X(~bool);
contour(X,Y,Z)
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