[R] plot multivariate function with known coefficient.

[YIHSU CHEN]

Dear R users --

I have a simple question that I cannot find the answers in the archive
email:  how to plot a multivariate function if I know the coefficients
already?  For instance, if I like to plot a 3D fig of Pi against X and
Y with the function Pi = a0 + a1X + a2Y, where a0, a1 & a2 are known.
Can "curve" do this?  So far, I have only seen univariate case.

Thank you.

Yihsu Chen