How can I create function that have char input arguments?

Hello everybody,

I made a function that caculates rotation in each axes.

 ==================================================================================
  function R=rot(dir,ang)

switch dir
        case 'x'
            R=[1 0 0 0;0 cos(ang) -sin(ang) 0;0 sin(ang) cos(ang) 0;0 0 0 1];
        case 'y'
            R=[cos(ang) 0 sin(ang) 0; 0 1 0 0;-sin(ang) 0 cos(ang) 0;0 0 0 1];
        case 'z'
            R=[cos(ang) -sin(ang) 0 0;sin(ang) cos(ang) 0 0;0 0 1 0;0 0 0 1];
        otherwise
            error=1;
end
==================================================================================

When I try to run this function, a error message shows like,

=================================================================
??? SWITCH expression must be a scalar or string constant.

Error in ==> rot at 3 switch dir =================================================================

I think I should make this function to recognize char input. How can I solve thie error?

Answer 1

[Wayne King]

How are you inputting dir to the function, are you inputting it as

'x', 'y', or 'z'?

It should work. I'm using direc below because dir is a MATLAB function name.

    direc = 'z';
    ang = pi/2;
    switch direc
      case 'x'
       R=[1 0 0 0;0 cos(ang) -sin(ang) 0;0 sin(ang) cos(ang) 0;0 0 0 1];
      case 'y'
        R=[cos(ang) 0 sin(ang) 0; 0 1 0 0;-sin(ang) 0 cos(ang) 0;0 0 0 1];
      case 'z'
        R=[cos(ang) -sin(ang) 0 0;sin(ang) cos(ang) 0 0;0 0 1 0;0 0 0 1];
     otherwise
        error('Direction not recognized');
    end

You should call the function like this:

   R = rot('x',pi/2);

for example

[Engstd]

Oops, I didn't known that 'dir' is a MATLAB function name.

You're answer helped a lot! Thanks!!!