rotating a 3D point around the y axis in matlab

Question

I have been provided with a rotation matrix to use:

and have entered the matrix into my function as

theta = radians(theta);
Ry(theta) = [cos(theta) 0 sin(theta); 0 1 0; -sin(theta) 0 cos(theta)];
newpose = pos*Ry(theta);

yet whenever the function reaches this stage it returns the error

??? Subscript indices must either be real positive integers or logicals.

any help much appreciated

Answer 1

The problem is the Ry(theta) . Call it something like Ry_theta if you want it to be a variable, or put it in an actual function. This should work:

theta = radians(theta);
Ry_theta = [cos(theta) 0 sin(theta); 0 1 0; -sin(theta) 0 cos(theta)];
newpose = pos*Ry_theta;

Or - if you want a more reusable solution:

% in your existing file:
theta = radians(theta);
newpose = pos*rotationAboutYAxis(theta);;

% in a file called rotationAboutYAxis.m:
function Ry = rotationAboutYAxis(theta)
Ry = [cos(theta) 0 sin(theta); 0 1 0; -sin(theta) 0 cos(theta)];

Answer 2

Ry(theta) 

theta最有可能不是实数或逻辑。