function [xm,ym]=rotxy(rm,tm)

% The function ROTXY transforms polar-vector field to xy-vector field.
% rm=rm(n_theda,n_r) must have the same dimension as tm.
%
% Calling sequence-
% [xm,ym]=rotxy(rm,tm)
%
% Input-
%	rm,tm		- vector field in polar coordinates
% Output-
%	xm,ym		- vector field in cartesian coordinates
 
% Z. Shen (Caltech)	March 1997

[n,k]=size(rm);
theta=linspace(0,2*pi-2*pi/n,n)';
xm=zeros(n,k);
ym=zeros(n,k);

for i1=1:n
   for j1=1:k
      xm(i1,j1)=rm(i1,j1)*cos(theta(i1))-tm(i1,j1)*sin(theta(i1));
      ym(i1,j1)=rm(i1,j1)*sin(theta(i1))+tm(i1,j1)*cos(theta(i1));
   end
end