How to plot with x in decreasing order?

Question

Sometimes y increases when x decreases:

from sympy import symbols, plot

p = symbols('p', positive=True)
h = (3.731444 - p**0.1902631) / 0.841728e-4

p_low = 150
p_high = 1013.25

plot(h, (p, p_low, p_high), axis_center=(p_low,0))

It can be more convenient to have a curve growing towards the top-right corner, it is possible to do that with sympy plot function?

I tried using reversed range and reversed extent without success.

Answer 1

It can be achieved by swapping the order of the xlim:

plot(h, (p, p_low, p_high), axis_center=(p_low,0), xlim=(max, min))

---

Using the plot's backend parameter you can access also to the matplolib backend. It has the advantage that you can inject your matplotlib commands. A subclass of BaseBackend is required. See source code of MatplotlibBackend for details.

Here an illustrative example:

import sympy.plotting.plot as plot
from sympy.plotting.plot import MatplotlibBackend
from sympy import symbols


class SwapXAxis(MatplotlibBackend):

    def show(self):
        # here matplolib code

        for ax in self.ax:
            # reverse scale on x-axis
            ax.invert_xaxis()
            # anchor the y-axis at the new origin
            ax.spines['right'].set_position('zero')
            # adjust labels and ticks
            ax.yaxis.set_ticks_position("right")
            ax.yaxis.set_label_position("right")

        # call parent method
        super().show()


p = symbols('p', positive=True)
h = (3.731444 - p**0.1902631) / 0.841728e-4

p_low = 150
p_high = 1013.25


plot(h, (p, p_low, p_high), backend=SwapXAxis, axis_center=(p_low,0))