【求助】关于等值线一问

[bbflying]

我想画z=1/x+1/y。，然后想知道x和y落入哪个区域时，z>=1；也就是说画等值线的时候，我想只画两条，对Z值做个判断，大于等于1还是小于1。这个应该怎么实现啊？谢谢大家了

[zhiwei]

>> clear all
>> [X,Y] = meshgrid(-2:.01:2,-2:.01:2);
>> Z=1./X+1./Y;
Warning: Divide by zero.
Warning: Divide by zero.
>> figure(1),mesh(X,Y,Z)
>> figure(2),contour(Z,1)
??? Error using ==> contourc
Contour levels must be finite.

Error in ==> specgraph.contourgroup.schema>LdoDirtyAction at 256
refresh(h);

??? Error occurred while evaluating listener callback.

>> figure(2),contour(Z,.99)