python数据分析2之numpy

 

 源代码

# -*- coding: utf-8 -*-
"""
Spyder Editor

This is a temporary script file.
"""

import numpy as np
a = np.array([1, 2, 3])
b = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
b[1,1]=10
print(a.shape)#3
print(b.shape)#(3,3)
print(a.dtype)#int32

import numpy as np
persontype = np.dtype({
    'names':['name', 'age', 'chinese', 'math', 'english'],
    'formats':['S32','i', 'i', 'i', 'f']})
peoples = np.array([("lisi",32,75,100, 90),("wangW",24,85,96,88.5),
       ("ZhaoYun",28,85,92,96.5),("HuangZhong",29,65,85,100)],
    dtype=persontype)
ages = peoples[:]['age']
chineses = peoples[:]['chinese']
maths = peoples[:]['math']
englishs = peoples[:]['english']
print(np.mean(ages))#计算平均值
print(np.mean(chineses))
print(np.mean(maths))
print(np.mean(englishs))

x1 = np.arange(1,11,2)
x2 = np.linspace(1,9,5)

x1 = np.arange(1,11,2)
x2 = np.linspace(1,9,5)
print(np.add(x1, x2))#[ 2.  6. 10. 14. 18.]
print(np.subtract(x1, x2))
#print(np.multiply((x1,x2)))
print(np.divide(x1, x2))
print(np.power(x1, x2))
print(np.remainder(x1, x2))


import numpy as np
a=np.array([[1,2,3],[4,5,6],[7,8,9]])
print(np.amin(a))#1
print(np.amin(a,0))#[1 2 3]
                  
print(np.amin(a,1)) #[1 4 7]
print(np.amax(a))#9
print(np.amax(a,0))#[7 8 9]
print(np.amax(a,1))#[3 6 9]

a = np.array([[1,2,3], [4,5,6], [7,8,9]])
print(np.ptp(a))#8 所有元素中最大和最小的差值
print(np.ptp(a,0))#[6 6 6]
print(np.ptp(a,1))#[2 2 2]

a = np.array([1,2,3,4])
wts = np.array([1,2,3,4])
print(np.average(a))#2.5
#print(np.average((a,weights=wts))

a = np.array([1,2,3,4])
print(np.std(a))
print(np.var(a))

a = np.array([[4,3,2],[2,4,1]])
print(np.sort(a))#每个子元素排序
print(np.sort(a, axis=None))#
print(np.sort(a, axis=0))  
print(np.sort(a, axis=1))