MATLAB Answers


Allocating 500 matrices into one 3D array with a loop

Asked by Zoe
on 19 Nov 2017
Latest activity Commented on by Zoe
on 20 Nov 2017
Hello guys, I have about 500 matrices naming after "yfit" + yr/month/date (such as yfit20000115). I want to save all of them into one 3d array, here is my code:
x = zeros(1455,1464,500);
x(:,:,1) = yfit20000115;
x(:,:,2) = yfit20000131;
x(:,:,3) = yfit20000216;
x(:,:,4) = yfit20000303;
x(:,:,5) = yfit20000319;
x(:,:,6) = yfit20000404;
........................ until x(:,:,500)
Can anybody please tell me how to loop through this? Especially, I do not know how to put the names into the loop. I thought about using EVAL, but eval's instruction on matlab seems very short and simple. Please help, thank you!


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They are all stored as variables in one .mat file. Thank you.
@Zoe: simply load the .mat file into one output variable (which is a structure), then loop over the fields of that structure. See Nicolas Schmit's answer to know how to do this.
Do NOT load 500 individual arrays into your workspace and then try to use eval to access them, unless you want to write slow, buggy, complex, inefficient, hard-to-debug code. Read this to why doing that is a very inefficient way to write code:
@Stephen Cobeldick: Thank you so much for telling me this! I read through the link and also sent the link to my professor!

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1 Answer

Answer by Nicolas Schmit on 20 Nov 2017
 Accepted Answer

S = load('your_mat_file');
To load your data into a structure S, Then loop over the fields of S.
fields = fieldnames(S);
x = zeros(1455,1464,500);
for k=1:500
x(:, :, k) = S.(f{k});


S = load('your_mat_file');
fields = fieldnames(S);
[fields, index] = sort(fields);
match = strncmp(fields, 'yfit', 4);
dataCell = struct2cell(S);
x = cat(3, dataCell{index});
I want to say thank you to both of you for being so helpful!!

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