define a function in which min() is used - function

Question

I am trying to define a function in which I want a part of the function limited. I try to do this by using min() but it returns
The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
My code:
def f(x, beta):
K_w = (1+((0.5*D)/(0.5*D+x))**2)**2
K_c = min(11,(3.5*(x/D)**(-0.5))) # <-- this is what gives me the problem. It should limit K_c to 11, but that does not work.
K_tot = (K_c**2+K_w**2+2*K_c*K_w*np.cos(beta))**0.5
return K_tot
x = np.linspace(0, 50, 100)
beta = np.linspace(0, 3.14, 180)
X, Y = np.meshgrid(x, beta)
Z = f(X, Y)
fig = plt.figure()
ax = plt.axes(projection='3d')
ax.contour3D(X, Y, Z, 100, cmap = 'viridis')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z');
I expected K_c to be limited to 11, but it gave a
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
I might be making a rookie mistake, but help is much appreciated!

Answer 1

Consider using np.clip of which its references can be found here.
np.clip(3.5*(x/D)**(-0.5), None, 11)
for your case.
For example,
>>> import numpy as np
>>> np.clip([1, 2, 3, 15], None, 11)
array([ 1, 2, 3, 11])
The problem with your code is that min is comparing a number with a list of which this is not expected.
Alternatively, here is a list comprehension approach:
A = [1, 2, 3, 15]
B = [min(11, a) for a in A]
print(B)