
Re: Quicker way to rotate a 3 dimensional array?
Posted:
Jan 27, 2013 11:48 PM


"Phil " <matlab@test.com> wrote in message <ke4thb$s7j$1@newscl01ah.mathworks.com>... > I've got an array that is three dimensional where the first two dimensions are relatively large numbers and the third has length 3. This third one contains x,y,z coordinates that I would like to rotate about the x axis. I've managed to do this using: > > tmp3 = tmp; > k = 0; > for i=1:height > for j=1:width > k = k + 1; > tmp3(i,j,:) = reshape(tmp(i,j,:),1,3)*[1,0,0;0,cos(theta),sin(theta);0,sin(theta),cos(theta)]; > end > end > > This works but as it's iterating, it's quite slow. Is there a faster way to do this?           Assuming theta is a scalar try this:
tmp3 = tmp; tmp3(:,:,2) = tmp(:,:,2)*cos(theta)tmp(:,:,3)*sin(theta); tmp3(:,:,3) = tmp(:,:,2)*sin(theta)tmp(:,:,3)*cos(theta);
Roger Stafford

