In SymPy you can automatically plot a surface from an expression, namely
from sympy import symbols
from sympy.plotting import plot3d
x, y = symbols('x y')
monkey_saddle = x**3 - 3*x*y**2
plot3d(monkey_saddle, cmap="RdYlBu")
to get
I could not find any kwarg that change the colormap. I know that I can create a lambdify and then directly make the plot using matplotlib. But I am curious if there is a way to do it directly in SymPy.
I read the source code of sympy.plotting.plot.py, it seems that the cmap is set to jet:
collection = self.ax.plot_surface(x, y, z,
cmap=self.cm.jet,
rstride=1, cstride=1,
linewidth=0.1)
You need to set the cmap of the collections object, and before calling plot3d() call unset_show() to disable calling pyplot.show():
from sympy import symbols
from sympy.plotting import plot3d
from sympy.plotting.plot import unset_show
unset_show()
x, y = symbols('x y')
monkey_saddle = x**3 - 3*x*y**2
p = plot3d(monkey_saddle)
p._backend.ax.collections[0].set_cmap("RdYlBu_r")
To get it working with the latest sympy version (1.7.1), I needed some small changes:
from sympy import symbols
from sympy.plotting import plot3d
from sympy.plotting.plot import unset_show
unset_show()
x, y = symbols('x y')
monkey_saddle = x ** 3 - 3 * x * y ** 2
p = plot3d(monkey_saddle)
p._backend.ax[0].collections[0].set_cmap("magma")
p._backend.ax[0].figure.show()
