Max of vector in higher dimensional array subject to constraints

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James Lee 2020-2-18

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https://ww2.mathworks.cn/matlabcentral/answers/506273-max-of-vector-in-higher-dimensional-array-subject-to-constraints

评论： Matt J 2020-2-19

Hello all,

I currently have code that's working but inefficient due to nested for loops, and I would like to vectorize it as possible. My data set is a higher dimensional array (a,b,.....z), and I'd like to find the maximum of each vector of z subject to a constraint based on the values of the other vectors.

For example, take a 3 dimensional array (a,b,c). I will have calculated a matrix (a x b-sized) of a constraint. I'd like to find a (a x b-sized) matrix that gives the maximum of each c vector that is measured only on the domain of (constraint:end). Let me know if there is a way to do this without for loops.

(edited for clarity)

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Answer 1

Matt J 2020-2-18

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https://ww2.mathworks.cn/matlabcentral/answers/506273-max-of-vector-in-higher-dimensional-array-subject-to-constraints#answer_416247

编辑：Matt J 2020-2-18

在 MATLAB Online 中打开

N=ndims(A); %A is the given matrix
z=size(A,N);  
idx=reshape(1:z, [ones(1,N-1),z] ) < constraint; %requires R2016b or higher
B=A;
 B(idx)=-inf;
result=max(B,[],N);

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James Lee 2020-2-19

Hey Matt,

This worked. I had to modify it a bit because I realized I had made a small mistake in the prompt (the constraint was an index to the matrix as opposed to a value) but this approach helped a lot. I appreciate it!