Ploting constant contours in the same color in matlab

问题

[x,y] = meshgrid(-10:1:10,-10:1:10); 
idx = (x~=0)&(y~=0);     
contour(x(idx)/(x(idx).^2+y(idx).^2).^(3/2),y(idx)/(x(idx).^‌2+y(idx).^2).^(3/2))‌​;

the output is white page!

回答1:

"delete" the points you do not want:

[x,y] = meshgrid(-10:0.1:10,-10:0.1:10);
Idontwantthis = (x.^2+y.^2)<1;
data= x./(x.^2+y.^2).^(3/2)+y./(x.^2+y.^2).^(3/2);
data(Idontwantthis)=NaN;
contourf(data,20);

Note that I replaced / by ./

I also added more points, as your meshgrid is tiny.

This is what the result looks like if you use contourf instead of contour (same thing, nicer looking):

来源：https://stackoverflow.com/questions/44305405/ploting-constant-contours-in-the-same-color-in-matlab