机器学习 番外篇 04 numpy之数组的合并和分割

数组的合并与分割

import numpy as np
x=np.array([1,2,3])
y=np.array([3,2,1])

x

>>>array([1, 2, 3])

y

>>>array([3, 2, 1])

np.concatenate([x,y]) # 拼接

>>>array([1, 2, 3, 3, 2, 1])

a=np.array([[1,2,3],
            [4,5,6]])

np.concatenate([a,a])

>>>array([[1, 2, 3],
       [4, 5, 6],
       [1, 2, 3],
       [4, 5, 6]])

np.concatenate([a,a],axis=1)

>>>array([[1, 2, 3, 1, 2, 3],
       [4, 5, 6, 4, 5, 6]])

z=np.array([666,66,66])

a1=np.concatenate([a,z.reshape(1,-1)])

a1

>>>array([[  1,   2,   3],
       [  4,   5,   6],
       [666,  66,  66]])

np.vstack([a,z])

>>>array([[  1,   2,   3],
       [  4,   5,   6],
       [666,  66,  66]])

b=np.full((2,2),100)

b

>>>array([[100, 100],
       [100, 100]])

np.hstack([a,b])

>>>array([[  1,   2,   3, 100, 100],
       [  4,   5,   6, 100, 100]])

分割

x=np.arange(10)

x

>>>array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

x1,x2,x3=np.split(x,[3,7])

x1

>>>array([0, 1, 2])

x2

>>>array([3, 4, 5, 6])

x3

>>>array([7, 8, 9])

x1,x2=np.split(x,[5])

x1

>>>array([0, 1, 2, 3, 4])

x2

>>>array([5, 6, 7, 8, 9])

arr=np.arange(16).reshape(4,4)

upper,lower=np.vsplit(arr,[2]) # 竖直分割

upper

>>>array([[0, 1, 2, 3],
       [4, 5, 6, 7]])

lower

>>>array([[ 8,  9, 10, 11],
       [12, 13, 14, 15]])

left,right=np.hsplit(arr,[2]) # 水平分割

left

>>>array([[ 0,  1],
       [ 4,  5],
       [ 8,  9],
       [12, 13]])

right

>>>array([[ 2,  3],
       [ 6,  7],
       [10, 11],
       [14, 15]])