Plotting a two variable function with two parameters in python

Question

I am trying to plot a 2 variable function with additional parameters which can be changed. Below is the function-

f(x,y) = (x - a*y)/(b+y)

I want to plot it in 3d and would like to see the change in the plot by changing the values of a and b, i.e. when a=1 and b=0, etc.

I can plot it for specific a and b cases, below is the code that works for a=1 and b=0. Is there any way where I don't need to map separately for different cases of a and b?

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
from matplotlib import cm
import numpy as np

x = np.linspace(30,7000,10000)
y = np.linspace(1,11000, 10000)

def delCAD(x,y):
    return (x-y)/(y) # the function when a=1 and b=0

fig = plt.figure(figsize=(12,8))
ax = Axes3D(fig)
ax = fig.gca(projection = "3d")
surf = ax.plot_trisurf(x, y, delCAD(x,y), cmap = cm.coolwarm)
fig.colorbar(surf, shrink=0.5, aspect=5)
plt.show()

look if this is usefull in your case [here](https://matplotlib.org/3.1.1/gallery/widgets/slider_demo.html) — Bruno Magacho, Jul 28 '21 at 05:24
@BrunoMagacho unfortunately the slider widget doesnt work in 3D — DrBwts, Jul 28 '21 at 12:17
You need to include your imports & all your code for instance `delCAD_con()` is missing — DrBwts, Jul 28 '21 at 12:22
@DrBwts [The slider widget DOES work in 3D](https://stackoverflow.com/a/41383374/2749397) — gboffi, Jul 28 '21 at 15:10

score 3 · Accepted Answer · answered Jul 28 '21 at 17:24

I generally use IPython or Jupyter for that sort of thing — maybe that's an option for you? For example, using ipywidgets.interact():

import matplotlib.pyplot as plt
import numpy as np
from ipywidgets import interact


x = np.linspace(1, 20, 50)
y = np.linspace(1, 20, 50)

y, x = np.meshgrid(y, x) 

def delCAD(x, y, a=1, b=0):
    return (x - a * y) / (b + y)

@interact(a=(1, 10), b=(0, 10))
def plot(a, b):
    fig, ax = plt.subplots(subplot_kw={"projection": "3d"}, figsize=(12, 6))
    surf = ax.plot_trisurf(x.flat, y.flat, delCAD(x, y, a, b).flat, cmap='coolwarm')
    fig.colorbar(surf, ax=ax, shrink=0.5, aspect=5)
    ax.view_init(elev=30, azim=160)
    plt.show()
    return

Produces this:

As well as the interact wrapper, I introduced the meshgrid line to compute all the locations in the grid, and I changed some of your parameters a bit so you can see more going on in the function. I hope you can unpick the various pieces to fit your needs.

Plotting a two variable function with two parameters in python

1 Answers1