Shading problem

Hello,

I have a problem with "shading interp". It doesn't work properly, if Idon't plot some additional points over it. Any help?

An example:

%%

n = 20;

data = randn(n);

x = linspace(-180,180,n);

y = linspace(-90,90,n);

figure(1);clf;hold on % Looks OK

pcolor(x,y,data);shading interp

plot(x,y,'w.','markersize',1);hold off % additional plotting

axis tight

figure(2);clf;hold on % Looks funny

pcolor(x,y,data);shading interp;hold off;axis tight

axis on

Janne