Extracting a matrix element which is within a cell containing cells.

Question

omid zandi 2021-3-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/774197-extracting-a-matrix-element-which-is-within-a-cell-containing-cells

评论： omid zandi 2021-3-16

采纳的回答： Stephen23

Sample.mat

在 MATLAB Online 中打开

Hi everybody.

I have a cell contaning cells, within each inner cell there is a matrix. By the way the aforementioned cell is attached. Now the question is that i want to extract the maximum value of a desired element of matrices. I have written a code, but does not seem to be an efficient one. does any can help me to make it more vectorized?

Thanks for your attention.

clc, clear, close all
% Loading mat file.
load('Sample.mat')
% Desired row and column.
Row = 5;
Col = 7;
% Preallocation.
Extracted = cell(length(Sample), 1);
Extracted(:) = {cell(12, 1)};
for yr = 1:length(Sample)
    for m = 1:12
        Extracted{yr,1}{m,1} = Sample{yr}{m}(Row,Col);
    end
end
% Finally converting cell to multidimensional array.
Extracted = cell2mat(cat(3,Extracted{:}));
% Finding max of all pages.
FinalOutput = max(max(Extracted, [], 3));

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omid zandi 2021-3-16

First: I run the profiler and attached the result screen shot, but can't get much out of it. How can it help? The point is that sample.mat in future can become much larger than what i have loaded right now. so later this code will put me in trouble.

Second: Thanks for your comments about loading to structure and not using clc, clear at the start of the code.

Rik 2021-3-16

If you click on 'Problem' that will take you to a breakdown of the runtime of that function where you can see which lines take the most time.

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Answer 1

Stephen23 2021-3-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/774197-extracting-a-matrix-element-which-is-within-a-cell-containing-cells#answer_649107

编辑：Stephen23 2021-3-16

在 MATLAB Online 中打开

Sample.mat

Putting scalar numeric data into nested cell arrays is pointlessly complex and inefficient. Get rid of the cell arrays:

S = load('Sample.mat');
% Desired row and column.
Row = 5;
Col = 7;
% Preallocation of one numeric matrix:
N = numel(S.Sample);
M = nan(N,12);
for yr = 1:N
    for m = 1:12
        M(yr,m) = S.Sample{yr}{m}(Row,Col);
    end
end
max(M(:))
ans = 63