How to create a 2D matrix with for loop iterating across a struct

Question

In a directory I have a collection of 20 files. I want to:

iterate a loop across those 20 files,
extract x and y data from them and
place those data in a 2D matrix that is created within the loop

Note below that files' is a 20x1 struct and file is a 1x1 struct.

I'm unsure how to build the 2-dimenstional matrix A inside such a loop.

I've tried something like

files = dir('./cases/*.dcm');

for file = files'

    [data extraction here, creating vars x and y]

    for k = 1:length(files')
        A(k,:) =  (x:y);
    end
end

but I get

Subscripted assignment dimension mismatch.

Any idea what I'm doing wrong?

Any idea what I'm doing wrong?, Nope, as I can't see the sizes of all things from here. This is however one of the most clear error messages MATLAB can throw at you, meaning your RHS has a different number of elements than the LHS. Check the sizes of all things — Adriaan
– Adriaan, Commented Dec 14, 2015 at 14:59
yes i agree with both of you, but can you give me any pointer on how one would go about creating a 2D matrix in this situation? I'll be glad to provide any specific info you need, I just don't know where to begin. — pepe
– pepe, Commented Dec 14, 2015 at 15:01
What do your files contain exactly? What are the sizes of x and y? — BillBokeey
– BillBokeey, Commented Dec 14, 2015 at 15:03
Are you saying that X and Y are just one number each? If so try files = dir('./cases/*.dcm');for k = numel(files);file = files(k);[data extraction here, creating vars x and y];A(k,:) = [x,y];end. — Jens Boldsen
– Jens Boldsen, Commented Dec 14, 2015 at 15:18

Jens Boldsen · Accepted Answer · 2015-12-15 10:30:08Z

1

This should work:

files = dir('./cases/*.dcm');
for k = 1:numel(files)
    file = files(k);
    %[data extraction here, creating vars x and y];
    A(k,:) = [x,y];
end

You might also want to add an initialization before the loop like:

A = zeros(numel(files),2);

answered Dec 15, 2015 at 10:30

Jens Boldsen

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