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Array assignments in a for loop - mt_reilly - Nov-23-2018
I am having difficulty trying to understand why two different expression in a for loop are producing the same result. In this case, I am doing numeric integration and differentiation as an exercise to learn some Python basics. But I am surprised to find that the produce the same values for different explicit assignments for y_int and yder. Inserted below is the Python code.
import numpy as np
import matplotlib.pyplot as plt
M = 101
x = np.linspace(-10, 10, num=M)
y = np.exp(-x**2)
y_int = np.zeros(M)
yder = y_int
plt.plot(x, y)
plt.show()
xs = range(x.size-1)
sm = 0
i = 0
for i in xs:
sm = sm + 0.5*(y[i]+y[i+1])*(x[i+1]-x[i])
y_int[i] = sm
yder[i] = (y[i+1]-y[i])/(x[i+1]-x[i])
plt.plot(x[1:x.size-1], y_int[1:x.size-1])
plt.show()
for i in xs:
yder[i] = (y[i+1]-y[i])/(x[i+1]-x[i])
print(sm)
plt.plot(x, yder)
plt.show()
del y_int
del yder
RE: Array assignments in a for loop - wavic - Nov-23-2018
How does line 17 is different from line 23?
17. yder[i] = (y[i+1]-y[i])/(x[i+1]-x[i]) 23. yder[i] = (y[i+1]-y[i])/(x[i+1]-x[i])
RE: Array assignments in a for loop - ichabod801 - Nov-23-2018
I think OP means that yder and y_int give the same graph.