numpy 矩阵对角线_numpy函数：[17]diag函数

今天用到的所有代码：

>>> numpy.diag((1,2,3))

array([[1, 0, 0],

[0, 2, 0],

[0, 0, 3]])

>>>

>>>

>>> x=numpy.arange(9).reshape((3,3))

>>> x

array([[0, 1, 2],

[3, 4, 5],

[6, 7, 8]])

>>>

>>>

>>> x=numpy.arange(10,19).reshape((3,3))

>>> x

array([[10, 11, 12],

[13, 14, 15],

[16, 17, 18]])

>>>

>>>

>>> y=numpy.diag(x)

>>> y

array([10, 14, 18])

>>>

>>>

>>>

>>> numpy.diag(x,1)

array([11, 15])

>>>

>>> numpy.diag(x,-1)

array([13, 17])

>>>

>>>

>>> numpy.diag(np.diag(x))

Traceback (most recent call last):

File "", line 1, in

numpy.diag(np.diag(x))

NameError: name 'np' is not defined

>>> numpy.diag(numpy.diag(x))

array([[10,  0,  0],

[ 0, 14,  0],

[ 0,  0, 18]])

>>>