MATLAB: How to concatenate arrays in loop

arrayconcatenateloopMATLAB

Dear Contributers,
There is a loop;
for i = 1:n;
X_rotate  = X.*cos(i*increment) - Y.*sin(i*increment);
Y_rotate  = X.*sin(i*increment) + Y.*cos(i*increment);
Helix  = [X_rotate(1:K1) ; Y_rotate(1:K1)];
fileID = fopen('helix_values.txt', 'w');
fprintf(fileID,'%f %f\n ', Helix);
fclose(fileID);
end
When open the text file, there just exists the last values of iteration X_rotate and Y_rotate. I need to collect the values for every iteration. I have tried to use cat command but I probably made mistake. How may I do that?
Thanks in advance.

Best Answer

It looks like your X and Y are row vectors of size [1, K1] (inferred from the line Helix = [X_rotate(1:K1) ; Y_rotate(1:K1)];). In that case you don't need to use a loop to calculate your X_rotate and Y_rotate:
steps = 1:n;
X_rotate = bsxfun(@times, X, cos(steps*increment)') - bsxfun(@times, Y, sin(steps*increments)');
Y_rotate = bsxfun(@times, X, sin(steps*increment)') + bsxfun(@times, Y, cos(steps*increments)');
%rows of X_rotate and Y_rotate correspond to steps
%columns correspond to the original X and Y values
I'm unclear how you want to save all the iterations onto the same text file though, columns of X and Y multiplied by the number of iterations?
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