how to save values for changing number of columns using "for loop "

I want to run a simple code, but i am unable to get the results correctly. A simple code is wriiten below, I am changing number of columns of one parameter. for that i want to save value of X_telda (10), X_telda(50) and X_telda(100) separately. U and X are given matrices.

for r=[10 50 100];
    X_telda=(U(:,1:r)*(U(:,1:r)'*X));
end

thank you

Answer 1

[KSSV]

r=[10 50 100] ; 
n = length(r) ; 
X_telda = cell(n,1) ; 
for i = 1:n
    X_telda{i} = (U(:,1:r(i))*(U(:,1:r(i))'*X));
end

X_telda is a cell, you can access it using X_telda{1},..etc

[Khan]

THANK YOU

Answer 2

[Walter Roberson]

We do not know the size of U. Call it N x M

U(:,1:r) is an N x r matrix

U(:,1:r)' is an r x N matrix.

X we do not know the size of, but in order to * it by an r x N matrix, we can tell that X must be N x something. Call it N x P

So U(:,1:r)' * X would be r x N * N x P giving r x P

U(:,1:r) * that would be N x r * r * P, so the overall operation would give N x P .

To put it another way, X_telda is size(U,1) by size(X,2)

Your code does not have any obvious problems, other than the fact that you are not storing the results X_telda before overwriting them in the next loop. But how do you want the multiple outputs represented?

Well, one way would be to use:

rvals = [10 50 100];
numr = length(rvals);
X_telda = zeros(size(U,1), size(X,2), numr);
for ridx = 1 : numr
   r = rvals(ridx);
   X_telda(:,:,ridx) = U(:,1:r)*(U(:,1:r)'*X));
end

[Khan]

Thank you