% Function trf (transformation)
%
% This mfile plots a rectangle with subrectangles in the left
% figure window, and its curvilinear image with images of the
% subrectangles in the right figure window. The transformation
% is (u,v) - > (x,y) = (f(u,v), g(u,v)).
% The call is trf(f,g,corners) when f and g are given as
% inline functions, and trf('f', 'g',corners) when f and g
% are given in mfiles.
% corners = [a b c d] is a vector of corner coordinates of
% the rectangle a < x < b, c < y