numpy矩阵的基础操作

import numpy #delimiter分隔符，dtype数据格式 word_alcho = numpy.genfromtxt("D:\qiujiahao4.txt",delimiter=",",dtype="str") #print (type(word_alcho)) print (word_alcho[0]) ['1' '2' '3' '4' 'qiu'] print (word_alcho[0][1]) 2 vector = numpy.array([5,10,15,20]) matrix = numpy.array([[5,10,15,20],[1,2,3,4]]) print (vector) print (matrix) print (word_alcho) [ 5 10 15 20] [[ 5 10 15 20] [ 1 2 3 4]] [['1' '2' '3' '4' 'qiu'] ['1' '2' '3' '4' 'qiu']] equal = (vector==10)&(vector==5) #数组中既等于10又等于5的 print (equal) equal = (vector==10)|(vector==5) vector[equal]=1 #将数组中等于10和5的值换成1 print (vector) print(matrix) equal = matrix[:,1]==10 #哪一行的第一列等于10 print (equal) matrix[equal,1]=1 #将这一行的第一列替换成1 print(matrix) [False False False False] [ 1 1 15 20] [[ 5 10 15 20] [ 1 2 3 4]] [ True False] [[ 5 1 15 20] [ 1 2 3 4]] print (matrix.dtype) print (vector[0:3]) #冒号代表所有行 print (matrix[:,1]) print (matrix[:,0:2]) int32 [ 1 1 15] [1 2] [[5 1] [1 2]] #U75代表utf类型 word_alcho = numpy.genfromtxt("D:\qiujiahao5.txt",delimiter=" ",dtype="U75",skip_header=1) print (word_alcho) [['qiu' 'man'] ['jia' 'woman']] vector = numpy.array(["1","2","3"]) print (vector.dtype) print (vector) vector = vector.astype(float) #将字符串转化成浮点型 print (vector.dtype) print (vector) print (vector.sum()) print (vector.mean()) #平均值 <U1 ['1' '2' '3'] float64 [ 1. 2. 3.] 6.0 2.0 matrix = numpy.array([[12,34,56,78],[11,22,33,44]]) sum = matrix.sum(axis=1) #指定维度，1代表行，0代表列 print(sum) [180 110] word_alcho = numpy.genfromtxt("D:\qiujiahao5.txt",delimiter=" ") print (word_alcho)#nan代表无法识别的 index = numpy.isnan(word_alcho[:,1])#判断是否是nan word_alcho[index,0:2]=0 print (word_alcho) print (word_alcho.sum()) print (word_alcho.mean()) [[ nan nan 123.] [ nan nan 456.]] [[ 0. 0. 123.] [ 0. 0. 456.]] 579.0 96.5