In keeping with the "There's only one obvious way to do it", how do you get the magnitude of a vector (1D array) in Numpy?
def mag(x): return math.sqrt(sum(i**2 for i in x))
The above works, but I cannot believe that I must specify such a trivial and core function myself.
The function you're after is
numpy.linalg.norm. (I reckon it should be in base numpy as a property of an array -- say
x.norm() -- but oh well).
import numpy as np x = np.array([1,2,3,4,5]) np.linalg.norm(x)
You can also feed in an optional
ord for the nth order norm you want. Say you wanted the 1-norm:
And so on.