%DIRSTRETCH  variable directional stretching of a complex vector%% DIRSTRETCH(X,D) where X is a complex vector and D a complex scalar stretches X by abs(D) along the direction arg(D)%   if D is a vector the same size as X, then X(i) is stretched by abs(D(i)) along the direction arf(D(i))% DIRSTRETCH(X,DIR,COEF) where X is a complex vector, DIR is either a unit modulus complex number or a real number and COEF a real number %   stretches X  by COEF along the direction DIR (or EXP(I*DIR) if DIR is real)%   if DIR and/or COEF is a vector the same size as X, then X(i) is stretched by COEF(i) along the direction DIR(i) (or EXP(I*DIR(i)))%% G. Rilling 3.2007% gabriel.rilling@ens-lyon.frfunction 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);