在numpy中获取索引 [英] getting indices in numpy

问题描述

有人可以找出下面的代码有什么问题吗?

Can someone find out what is wrong with the code below?

import numpy as np
data = np.recfromcsv("data.txt", delimiter=" ", names=['name', 'types', 'value'])
indices = np.where((data.name == 'david') * data.types.startswith('height'))
mean_value = np.mean(data.value[indices])

我要计算大卫的体重和身高的平均值，并标记如下:

I want to calculate mean of weight and height for david and mark as follows:

david>> mean(weight_2005 and weight_2012), mean (height_2005 and height_2012)
mark>> mean(weight_2005 and weight_2012), mean (height_2005 and height_2012)

从文本(data.txt)文件中:

From the text (data.txt) file:

david weight_2005 50
david weight_2012 60
david height_2005 150
david height_2012 160
mark weight_2005 90
mark weight_2012 85
mark height_2005 160
mark height_2012 170

我正在使用python 3.2和numpy 1.8

I am using python 3.2 and numpy 1.8

上面的代码提供了如下类型错误:

The above code provides the type error as follows:

TypeError: startswith first arg must be bytes or a tuple of bytes, not numpy.str_

推荐答案

使用Python3.2和numpy 1.7，此行有效

With Python3.2 and numpy 1.7, this line works

indices = np.where((data.name == b'david') * data.types.startswith(b'height'))

data显示为:

rec.array([(b'david', b'weight_2005', 50),...], 
      dtype=[('name', 'S5'), ('types', 'S11'), ('value', '<i4')])

type(data.name[0])是<class 'bytes'>.

b'height'也可以在Python2.7中使用.

b'height' works in Python2.7 as well.

另一种选择是将所有数据转换为unicode(Python 3字符串)

another option is to convert all the data to unicode (Python 3 strings)

dtype=[('name','U5'), ('types', 'U11'), ('value', '<i4')]
dataU=data.astype(dtype=dtype)
indices = np.where((dataU.name == 'david') * dataU.types.startswith('height'))

或

data = np.recfromtxt('data.txt', delimiter=" ", 
    names=['name', 'types', 'value'], dtype=dtype)

看起来recfromcsv不需要dtype，但是recfromtxt可以.

It looks like recfromcsv does not take a dtype, but recfromtxt does.

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