c2_1_3.m

该文件主要包括了matlab的一些主要应用例程!对学习matlab很有帮助

%filename:c2_1_3.m
f=vectorize(inline('x*y*exp(-x*x-y*y)','x','y'));
fx=vectorize(inline('(1-2*x*x)*y*exp(-x*x-y*y)','x','y'));
fy=vectorize(inline('(1-2*y*y)*x*exp(-x*x-y*y)','x','y'));
x=-1:0.1:1;
y=x;
[X,Y]=meshgrid(x,y);
F=f(X,Y);
[dfx,dfy]=gradient(F,0.1);
dfx3=diff3p(F,0.1);
dfy3=diff3p(F,0.1,1,2);
DFX=fx(X,Y);
DFY=fx(X,Y);
DF=DFX*0.1+DFY*0.1;
err1=norm(dfx-DFX)+norm(dfy-DFY);
err2=norm(dfx3-DFX)+norm(dfy3-DFY);
subplot(221) %figure(1);%
surf(X,Y,F,DF);
title('y=f(x,y)')
			subplot(222)
			quiver(X,Y,DFX,DFY);
			title('true case')
subplot(223)
quiver(X,Y,dfx,dfy);
title('gradient')
			subplot(224)
			quiver(X,Y,dfx3,dfy3);
			title('diff3p')