您如何获得Numpy中向量的大小? [英] How do you get the magnitude of a vector in Numpy?

问题描述

与只有一种明显的方法"相一致，如何在Numpy中获得矢量(一维数组)的大小?

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))

以上方法有效，但我不相信，我必须自己指定这样一个琐碎且核心的功能.

The above works, but I cannot believe that I must specify such a trivial and core function myself.

推荐答案

您追求的功能是

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)

您还可以输入所需的n阶范数的可选ord.假设您想要1个标准:

You can also feed in an optional ord for the nth order norm you want. Say you wanted the 1-norm:

np.linalg.norm(x,ord=1)

以此类推.

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