Re: Create & Calling list of Matrix name

[Andrew Janke]

On 3/1/19 5:39 PM, quocphantruong wrote:
> Hello
> My problem is about naming and calling set of matrix name using loop
> 1. Let say I have a large matrix X(100x2). Now I want to cut this matrix
> into 20 sub-matrixes and naming them from A1 to A20, each has size(5x2)
>
> 2. Then I need to perform some operation hence, need to call out matrix Ai
> (for i=1:20) then how should I call them out in loop.
>
> I search and there is some solution:
>    for i = 1:20
>      eval (sprintf ("A%d = %d;", i, i));
>    endfor
>
> Howevever, this seems does not work with matrix. And I dont get how the code
> is doing, if you could help me explain that would be great
> THank you
> Phan

Working with multiple named variables using sprintf() and eval() is only 
going to bring you unhappiness. Instead of using 20 variables named A1, 
A2, ... A20, try using a single 20-long cell array named A, which you 
can index as A{1}, A{2},  ... A{20}.

For example:

X = meshgrid (1:2, 1:100);
n = 20;
A = mat2cell(X, repmat(n, [size(X,1)/n 1]), 2);

Now you can loop over them and do things like:

B = cell (size (A));
for i = 1:numel (A)
   B{i} = some_operation (A{i});
endfor

Or, more concisely, use cellfun:

B = cellfun (@(x) {some_operation (x)}, A);

Cheers,
Andrew