请问画三维曲面图时，​如果自变量的区间边界​是一个函数怎么办？

例如，用surf(X,Y,Z)画函数z(x,y)=x+y的三维曲面图，在XOY平面的范围是x=1,y=0,x=y围成的三角形区域，该怎么办？

Answer 1

[Rik]

Use meshgrid or ndgrid to generate a full grid of coordinates. Then you mark all points outside your triangle with inpolygon. The surf function will ignore NaN values, so that is good choice.

You can make the grid as fine as you need it to be.

[X,Y]=ndgrid(linspace(0,1,50));
Z=X+Y;

%define the triangle here
xv=[0 1 1];
yv=[0 0 1];

L=inpolygon(X,Y,xv,yv);
X(~L)=NaN;
Y(~L)=NaN;
Z(~L)=NaN;

surf(X,Y,Z)