This should be extremely easy, I want to make a nice colour plot of a 2d function where colour denotes the function value.
I can do
y=var('y')
f=y^2
plot(f)
and I get a nice plot.
If I try
y=var('y')
f=y^2+x^2
plot(f)
Then sage tells me it can't find the variable y. Which is ridiculous, since y is in the same place as when I tried to plot a 1d function of y. Anyway, I tried googling to find a function within sage to achieve this (without resorting to excessive matplotlib syntax) and had no success so thought I'd ask a question here. Intuitively the first case is hardly more complicated than the second case so there should be a simple function that can realize this for me.
Many thanks!