Question

I’d like to plot a function of format a*y**3 + b(x)*y**2 + c(x)*y + d(x) in gnuplot.

Edit: To clear out what I’m trying to plot, these are the expressions for b(x), c(x), d(x):

b(x) = b1 + b2*x
c(x) = c1 + c1*x + c2*x**2
d(x) = d1 + d1*x + d2*x**2 + d3*x**3

a, b1, ... , d2, d3 are constants, which I know.

I was wondering if there’s any way to give gnuplot a f(x,y) function and it would figure out (numerically) the plot.

Edit 2: Doing stuff in the middle of the night is not always a good idea… Obviously what I was requesting would be surface levels, but in fact I’m interested in plotting f(x,y) = 0

Answer 1

I got it:

set contour
unset surface
set view map
set cntrparam levels discrete 0
splot a*y**3 + b(x)*y**2 + c(x)*y + d(x)