Rotating a 2 demential shape 30 degrees counter clockwise

Hello. I am new to the Matlab community and I was having a bit of trouble rotating an irregular 2 dimensional shape. The coordinates a x = [0 0 2 2 0 -2 -2 0] and y = [0 2 2 3 5 3 1 0]. I have to rotate this 30 degrees counter clockwise on the same axis. Any suggestions? Thanks

Answer 1

[Alex]

This should rotate the points 30 degrees. R is using the rotation matrix to update the pairs of x,y coordinates.

z = [x; y];

thetad = 30;

R =[cosd(thetad) -sind(thetad); sind(thetad) cosd(thetad)];

for i = 1: 8

z(:,i) = R * z(:,i);

end

plot(z(1,:),z(2,:))

Here's another post that does it a little differently: http://www.mathworks.com/matlabcentral/answers/296860-rotating-a-2d-shape?s_tid=answers_rc1-1_p1

[Alex]

You can also use makehgtform to get the rotation matrix, which could be useful if you needed to perform more transformations on the matrix at once. Just make sure you convert your degrees to radians.

Example:

z = [x;y];

M = makehgtform('zrotate', (pi/6));

for i = 1:8

z(:,i) = M(1:2,1:2) * z(:,i);

end

plot(z(1,:),z(2,:))

Here's some more info for working with makehgtform: http://www.mathworks.com/help/matlab/ref/makehgtform.html