Automatically put content of structure fields in a matrix

Hi all,

For the following structure:

A.TEST=rand(15x8);
A.TEST1=rand(15x8);
A.TEST2=rand(15x8);
A.TEST3=rand(15x8);
A.TEST4=rand(15x8);
A.TEST5=rand(15x8);

I would like to find an optimal way to create a new matrix (let's say B) that contains all values from TEST to TEST5 concatenated vertically, which would be B = (15*5,8).

Preferabally automatically, since my real dataset is much bigger.

Thanks!

[Stephen23]

Better data design would make your code simpler too, e.g. a non-scalar structure:

A.S(1).TEST = rand(15,8)
A.S(2).TEST = rand(15,8)
A.S(3).TEST = rand(15,8)
A.S(4).TEST = rand(15,8)
A.S(5).TEST = rand(15,8)
M = vertcat(A.S.TEST) % <- this is all you need

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

[Inti Vanmechelen]

I've changed my structure towards your proposal. Indeed easier.

I'm learning everyday, thanks for the tip!

Answer 1

[darova]

Try getfield

fnames = fieldnames(A);
B = [];
for i = 1:length(fnames)
    b1 = getfield(A,fnames{i});
    B = [B; b1];
end

Use preallocation if for loop is slow

[Inti Vanmechelen]

Hi Darova,

Thank you for your help!

This solution worked, but unfortunately, I have an extra field in the structure (should've probably added that from the beginning).

Do you know how to get the same command with a structure like this?

A.S.TEST = rand(15,8)
A.S.TEST1 = rand(15,8)
A.S.TEST2 = rand(15,8)
A.S.TEST3 = rand(15,8)
A.S.TEST4 = rand(15,8)

Where S varies from 1 to 20 and TEST varies from TEST to TEST4.

I tried to figure it out but can't seem to find the correct solution.

Thank you,

Inti

[darova]

Use nested for loop

fnames = fieldnames(A);
B = [];
for i = 1:length(fnames)    
    b1 = getfield(A,fnames{i});
    s = whos('b1');
    if strcmp('struct',s.class)     % if type of variable is 'struct'
        fnames1 = fieldnames(b1);        
        for j = 1:length(fnames1)
            b2 = getfield(b1,fnames1{j});
            B = [B; b2];
        end
    else
        B = [B; b1];
    end
end