max function within integrate.quadrature fails

Question

The following basic Python script fails:

from scipy import integrate
integrate.quadrature(lambda t: max(1,t), -2, 2)[0]

with the error message:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

It looks to me that the integrate.quadrature command does not like the max function but I do not understand why.

Asked By: pluton

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Answer 1

scipy is not passing a scalar or 1-element array to your function, so it needs to be vectorized:

from scipy import integrate
import numpy as np

integrate.quadrature(lambda t: np.maximum(1, t), -2, 2)[0]

You will get a warning like

AccuracyWarning: maxiter (50) exceeded. Latest difference = 6.366377e-04

However, the result will be close to the expected value of 4.5:

4.499480255789206

Here is a plot for reference:

t = np.linspace(-2, 2, 100)
plt.plot(t, np.maximum(1, t))

Question: