numpy创建矩阵常用方法
arange+reshape
in:
n = np.arange(0, 30, 2)# start at 0 count up by 2, stop before 30
n = n.reshape(3, 5) # reshape array to be 3x5- 1
- 2
out:
linspace+resize
in：
o = np.linspace(0, 4, 9)
o.resize(3, 3)- 1
- 2
out:
notice:reshape与resize区别
ones zeros eye diag random.randint等创建矩阵
in：
np.ones((3, 2))
np.zeros((2, 3))
np.eye(3)#3维单位矩阵
y = np.array([4, 5, 6])
np.diag(y)#以y为主对角线创建矩阵
np.random.randint(0, 10, (4,3))- 1
- 2
- 3
- 4
- 5
- 6
out：
ones:
[[ 1. 1.]
[ 1. 1.]
[ 1. 1.]]
zeros:
[[ 0. 0. 0.]
[ 0. 0. 0.]]
eye:
[[ 1. 0. 0.]
[ 0. 1. 0.]
[ 0. 0. 1.]]
diag:
[[4 0 0]
[0 5 0]
[0 0 6]]
randint
[[1 3 5]
[4 4 3]
[9 3 0]
[7 0 0]]
矩阵拼接
in:
p = np.ones([2, 3], int)
np.hstack([p, 2*p])#水平拼接
np.vstack([p, 2*p])#竖直拼接- 1
- 2
- 3
out:
hstack：
[[1 1 1 2 2 2]
[1 1 1 2 2 2]]
vstack:
[[1 1 1]
[1 1 1]
[2 2 2]
[2 2 2]]
备注:
1 矩阵常用操作:
>>> b1 = array([[1,2,3],[4,5,6],[7,8,9]])
>>> b1[1:2]
array([[4, 5, 6]])