numpy:TypeError中的错误:只能将长度为1的数组转换为Python标量 [英] error in numpy:TypeError: only length-1 arrays can be converted to Python scalars

问题描述

我写了一个函数sigmoid:

I write a function sigmoid:

def sigmoid(inX):
    return 1.0 / (1 + exp(-inX))

并且当inX是100x1大小的矩阵时，会出现错误:

and when the inX is a matrix of 100x1 size, the error arises:

/home/abyss/python/machine/logistic/logReg.py in sigmoid(inX)
     12 
     13 def sigmoid(inX):
---> 14     r = 1.0 / (1 + exp(-inX))
     15     return r
     16 

TypeError: only length-1 arrays can be converted to Python scalars

但是我可以在命令行中直接使用此表达式:

but I can directly use this expression in command line:

In [59]: r = 1.0 / (1 + exp(-h))

In [60]: shape(r)
Out[60]: (100, 1)

我很困惑，这是怎么发生的?

I am totally confused, how did this happen?

推荐答案

当采用数组或其他不想使用Python数学库的指数时，请改用NumPy库:

When you are taking the exponent of an array or anything else you don't want to use Python's math library, use NumPy library instead:

import numpy as np
def sigmoid(inX):
    r = 1.0/(1+ np.exp(-inX))
    return r

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