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

def sigmoid(intX): return 1.0/(1+exp(-intX)) dataMatrix = mat(dataMatIn) weights = ones((n, 1)) h = sigmoid(dataMatrix*weights)

出错：

return 1.0/(1+math.exp(-intX)) TypeError: only length-1 arrays can be converted to Python scalars

因为dataMatrix 与weights均为numpy矩阵，相乘也是numpy矩阵，而math.exp()函数只处理python标准数值。
此处需要用numpy的exp()方法，如下：

import numpy as np def sigmoid(self, intX): return 1.0/(1+np.exp(-intX))

【TypeError: only length-1 arrays can be converted to Python scalars】也可以在文件头添加from numpy import *,就可以直接用exp(-intX)了

def smoSimple(dataMatIn, classLabels, C, toler, maxIter): dataMatrix = mat(dataMatIn) labelMat = mat(classLabels).transpose() iter = 0 while iter < maxIter: alphaPairChanged = 0 for i in range(m): fXi = float(multiply(alphas, labelMat).T * (dataMatrix * dataMatrix[i,:].T)) + b .....

出错：