%% Viewing a Penny
% The file PENNY.MAT contains measurements made at the National Institute of
% Standards and Technology of the depth of the mold used to mint a U. S. penny,
% sampled on a 128-by-128 grid.
% 
% Copyright 1984-2002 The MathWorks, Inc. 
% $Revision: 5.7 $  $Date: 2002/04/15 03:36:21 $

%% Drawing a contour plot
% Draw a contour plot with 15 copper colored contour lines.

load penny.mat
contour(P,15)
colormap(copper)
axis ij square


%% Drawing a pseudocolor plot
% Draw a pseudocolor plot with brightness proportional to height.

pcolor(P)
axis ij square
shading flat


%% Drawing a pseudocolor plot with a colormap
% Draw a pseudocolor plot with brightness proportional to the Laplacian of the
% height. A cell is bright if its height is greater than the average of its
% four neighbors and dark if its height is less than the average of its four
% neighbors. This is an unusual "lighting model", but it produces an image
% that looks like a photograph of a penny.

D = -del2(P);
pcolor(D)
axis ij square
shading flat


%% Drawing a surface plot with a colormap
% Finally, produce a 3-D, copper colored, surface plot with the Laplacian
% lighting model.

surf(P,D);
axis('ij','tight')
shading('flat')
view(-20,75)