Extract max value and corresponding index from a cell into seperate matrixes in a for loop

Question

Stephen Lesko 2023-6-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1989793-extract-max-value-and-corresponding-index-from-a-cell-into-seperate-matrixes-in-a-for-loop

评论： Stephen Lesko 2023-6-29

Hi, I want to extract the index and max value from a cell containing vectors. Currently when I run this code it saves the max stress and index as just a variable rather than a matrix of each vectors max and index.

peak_stress = [];
stress = [];
index = [];
for p=1:numel(sigma)
    peak_stress = [peak_stress, max(sigma{1,p}(1:end))]; %saves max stress as a vector (works fine)
    [stress,index] = max(sigma{1,p}(1:end));  %goal: create a matrix for stress and a matrix for index from sigma cell sigma{1xn}(n,1)
end

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Stephen23 2023-6-29

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

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Answer 1

Jayant 2023-6-29

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1989793-extract-max-value-and-corresponding-index-from-a-cell-into-seperate-matrixes-in-a-for-loop#answer_1264838

在 MATLAB Online 中打开

What I understood from you question is that you want to store the max stress and index.

These values can be appended to the stress and index matrices using the concatenation operator (;).

for p=1:numel(sigma)
    peak_stress = [peak_stress, max(sigma{1,p}(1:end))]; %saves max stress as a vector (works fine)
    [stress,index] = max(sigma{1,p}(1:end));  %goal: create a matrix for stress and a matrix for index from sigma cell sigma{1xn}(n,1)
     % Append the values to the matrices
    stress = [stress; max_stress]; 
    index = [index; max_index];
end

After the loop, the stress matrix will contain the maximum stress values from each vector, and the index matrix will contain the corresponding indices.

I hope this helps.

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Stephen Lesko 2023-6-29

This idea makes sense, but when I tried implementing the code it the stress and index are still being saved as values rather than a matrix.

Stephen Lesko 2023-6-29

在 MATLAB Online 中打开

It works with a slight naming change to loop.

for p=1:numel(sigma)
    peak_stress = [peak_stress, max(sigma{1,p}(1:end))]; %saves max stress as a vector (works fine)
    [max_stress,max_index] = max(sigma{1,p}(1:end));  %goal: create a matrix for stress and a matrix for index from sigma cell where sigma{1xn}(n,1)
    % Append the values to the matrices
    stress = [stress, max_stress]; 
    index = [index, max_index];
end