function [xout,yout] = xfm1(xin,yin,theta,x_offset,y_offset)
% Program to rotate and translate x,y values from x",y" to x,y space.
% Written to plot hyperbolas for time of arrival code.
% theta value assumed to be in radians.

%  rotation matrix
xfm = [cos(theta) sin(theta); ...
      -sin(theta) cos(theta)];
% make x,y values into a column vector
r_in = [xin; yin];
% rotate 
r_out = xfm*r_in;
x = r_out(1,:); y = r_out(2,:);
xout = x + x_offset; 
yout = y + y_offset;