extract values from function used by odeint scipy python

Question

I have the following script to calculate dRho using odeint.

P_r = 10e5
rho_r = 900
L = 750
H = 10
W = 150
A = H * W
V = A * L
fi = 0.17

k = 1.2e-13
c = 12.8         


        

Answer 1

The following could be what you want. You could store the intermediate values in a list and later plot that list. That would require to store the x values as well.

import numpy as np
import matplotlib.pyplot as plt
from scipy.integrate import odeint

xs = []
yd = []

def dY(y, x):
    a = 0.001
    yin = 1
    C = 0.01
    N = 1
    dC = C/N
    b1 = 0
    y_diff = -np.copy(y)
    y_diff[0] += yin
    y_diff[1:] += y[:-1]
    xs.append(x)
    yd.append(y_diff)
    return (a/dC)*y_diff+b1*dC

x = np.linspace(0,20,1000)
y0 = np.zeros(4)
res = odeint(dY, y0, x)

plt.plot(x,res, '-')

plt.gca().set_prop_cycle(plt.rcParams['axes.prop_cycle'])
plt.plot(np.array(xs),np.array(yd), '-.')

plt.show()

Dotted lines are the respective y_diff values for the res solutions of the same color.