Numpy的array数组操作

Numpy的array数组操作

import numpy
world_alcohol = numpy.genfromtxt("E:\machinelearning\machinelearninginaction\Ch02\datingTestSet.txt",delimiter="\t")
print(type(world_alcohol))
world_alcohol

import numpy
world_alcohol = numpy.genfromtxt("E:\machinelearning\machinelearninginaction\Ch02\datingTestSet.txt",delimiter="\t",dtype='str')
print(type(world_alcohol))
world_alcohol

#去掉第一行
import numpy
world_alcohol = numpy.genfromtxt("E:\machinelearning\machinelearninginaction\Ch02\datingTestSet.txt",delimiter="\t",dtype='U75',skip_header=1)
print(type(world_alcohol))
world_alcohol

#向量（一维数组）
vector = numpy.array([5,10,15,20])
print vector
vector.dtype
#前三个
print(vector[0:3])
print(vector[0:1])

#二维数组
matrix = numpy.array(
[
[54563546,1056786,15635465],[27860,22896789,36872],[50006000,68400000000,45400000000000]
]
)
print matrix
#科学计数法该如何表示呢？
#所有行的第一列
print '=============================================================='
print matrix[:,1]
#所有行的前两列
print matrix[:,0:2]