numpy.diag¶

numpy.diag(v,k=0)[source]¶

Extract a diagonal or construct a diagonal array.

See the more detailed documentation fornumpy.diagonal if you use thisfunction to extract a diagonal and wish to write to the resulting array;whether it returns a copy or a view depends on what version of numpy youare using.

Parameters:	v:array_like Ifv is a 2-D array, return a copy of itsk-th diagonal.Ifv is a 1-D array, return a 2-D array withv on thek-thdiagonal. k:int, optional Diagonal in question. The default is 0. Usek>0 for diagonalsabove the main diagonal, andk<0 for diagonals below the maindiagonal.
Returns:	out:ndarray The extracted diagonal or constructed diagonal array.

See also

diagonal

Return specified diagonals.

diagflat

Create a 2-D array with the flattened input as a diagonal.

trace

Sum along diagonals.

triu

Upper triangle of an array.

tril

Lower triangle of an array.

Examples

>>>x=np.arange(9).reshape((3,3))>>>xarray([[0, 1, 2],       [3, 4, 5],       [6, 7, 8]])

>>>np.diag(x)array([0, 4, 8])>>>np.diag(x,k=1)array([1, 5])>>>np.diag(x,k=-1)array([3, 7])

>>>np.diag(np.diag(x))array([[0, 0, 0],       [0, 4, 0],       [0, 0, 8]])