How can I create structure entries in a for loop.?

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Allen Hammack
Allen Hammack 2022-1-8
评论： Allen Hammack 2022-1-12
I have multiple data sets. For each data set, I would like to perform multiple calculations and have the results of those calculations be entries in a structure. For instance, say I have three data sets for which I'd like to calculate the maximum and minimum values and create entries in a fields in a structure for each maximum and minimum. I'm currently doing these calculations for each data set separately without a for loop, and my code is repetitive. I think I should be able to do this, but I haven't been able to figure out how. I think my code should look something like this:
data = [data1 data2 data3]
for j = length(data)
s.data(j)_max = max(data(j))
s.data(j)_min = min(data(j))
end
I don't know how to create the fields - s.data(j)_max and s.data(j)_min - of the the structure s using the entires in the array data. Can someone please help me?

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Stephen23
Stephen23 2022-1-8
编辑：Stephen23 2022-1-10
Using a cell array and a structure array:
C = {data1,data2,data3};
for k = 1:numel(C)
S(k).max = max(C{k});
S(k).min = min(C{k});
end
Or one structure array (more robust, recommended):
S = struct('data',{data1,data2,data3});
for k = 1:numel(S)
S(k).max = max(S(k).data);
S(k).min = min(S(k).data);
end
https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html
https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html
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Stephen23
Stephen23 2022-1-12
编辑：Stephen23 2022-1-12
Ran in:
It is simpler to use the %d format specifier, rather making things more complex by adding slow NUM2STR:
sprintf('%d_max',k)
% ^ ^
"Your obfuscated code also works with a slight modification."
Structure fieldnames must start with a letter, so your modification will not work:
S = struct();
S.(sprintf('%d_max',2)) = pi
Invalid field name: '2_max'.
Using the fieldnames that I showed you however does work, as they have leading letters.
Allen Hammack
Allen Hammack 2022-1-12
Thank you for the suggestion about num2str being slow. I replaced num2str with your suggestion of using %d, and the script is much faster.

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