%DIRSTRETCH variable directional stretching of a complex vectorfunction y=dirstretch(x,dir,coef)if nargin == 3   if ~isreal(dir) && all(abs(dir) ~= 1)    warning('non unit modulus of direction argument ignored')  end  if isreal(dir) && any(abs(dir) ~= 1)    dir = exp(i*dir);  end  if any(dir==0)    error('invalid zero direction argument')  end  tmp = abs(dir);  tmp(tmp==0) = 1; % to avoid NaNs  dir = dir./tmp;endif nargin == 2    coef = abs(dir);    tmp = coef;    tmp(coef==0) = 1; % to avoid NaNs    dir = 1./tmp.*dir;endrotx = x.*conj(dir);y = coef.*dir.*real(rotx)+i*dir.*imag(rotx);