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Python numpy生成矩阵、串联矩阵

2016-05-11 13:13 274 查看
import numpy

生成numpy矩阵的几个相关函数:

numpy.array()

numpy.zeros()

numpy.ones()

numpy.eye()

串联生成numpy矩阵的几个相关函数:

numpy.array()

numpy.row_stack()

numpy.column_stack()

numpy.reshape()

>>> import numpy
>>> numpy.eye(3)
array([[ 1.,  0.,  0.],
[ 0.,  1.,  0.],
[ 0.,  0.,  1.]])
>>> numpy.zeros(3)
array([ 0.,  0.,  0.])
>>> numpy.ones(3)
array([ 1.,  1.,  1.])
>>> x1 = numpy.array((1, 2, 3))
>>> x1
array([1, 2, 3])
>>> x2 = numpy.array([4, 5, 6])
>>> x2
array([4, 5, 6])
>>> x3 = numpy.array((x1, x2))
>>> x3
array([[1, 2, 3],
[4, 5, 6]])
>>> x4 = x3.reshape(2, 3)
>>> x4
array([[1, 2, 3],
[4, 5, 6]])
>>> x4 = x3.reshape(3, 2)
>>> x4
array([[1, 2],
[3, 4],
[5, 6]])
>>> x5 = numpy.row_stack(x1, x2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: vstack() takes exactly 1 argument (2 given)
>>> x5 = numpy.row_stack((x1, x2))
>>> x5
array([[1, 2, 3],
[4, 5, 6]])
>>> x6 = numpy.row_stack([x1, x2])
>>> x6
array([[1, 2, 3],
[4, 5, 6]])
>>> x7 = numpy.row_stack((x6, x2))
>>> x7
array([[1, 2, 3],
[4, 5, 6],
[4, 5, 6]])
>>> x7[0]
array([1, 2, 3])
>>> x7[1]
array([4, 5, 6])
>>> x7[2]
array([4, 5, 6])
>>> x8 = numpy.column_stack([x1, x2, x1, x2])
>>> x8
array([[1, 4, 1, 4],
[2, 5, 2, 5],
[3, 6, 3, 6]])
>>> x8[0]
array([1, 4, 1, 4])
>>> x8[1]
array([2, 5, 2, 5])
>>> x8[2]
array([3, 6, 3, 6])
>>> x8[3]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IndexError: index 3 is out of bounds for axis 0 with size 3
>>> x8[0][3]
4
>>>
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