Python - 如何找到下三角形numpy矩阵的方阵？ （对称的上三角形）

I generated a lower triangular matrix, and I want to complete the matrix using the values in the lower triangular matrix to form a square matrix, symmetrical around the diagonal zeros.

我生成了一个下三角矩阵，我想用下三角矩阵中的值完成矩阵，形成一个方阵矩阵，围绕对角零点对称。

lower_triangle = numpy.array([
[0,0,0,0],
[1,0,0,0],
[2,3,0,0],
[4,5,6,0]])

I want to generate the following complete matrix, maintaining the zero diagonal:

我想生成以下完整矩阵，保持零对角线：

complete_matrix = numpy.array([
[0, 1, 2, 4],
[1, 0, 3, 5],
[2, 3, 0, 6],
[4, 5, 6, 0]])

Thanks.

谢谢。

2 个解决方案

#1

You can simply add it to its transpose:

您只需将其添加到其转置：

>>> m
array([[0, 0, 0, 0],
       [1, 0, 0, 0],
       [2, 3, 0, 0],
       [4, 5, 6, 0]])
>>> m + m.T
array([[0, 1, 2, 4],
       [1, 0, 3, 5],
       [2, 3, 0, 6],
       [4, 5, 6, 0]])

#2

You can use the numpy.triu_indices or numpy.tril_indices:

您可以使用numpy.triu_indices或numpy.tril_indices：

>>> a=np.array([[0, 0, 0, 0],
...             [1, 0, 0, 0],
...             [2, 3, 0, 0],
...             [4, 5, 6, 0]])
>>> irows,icols = np.triu_indices(len(a),1)
>>> a[irows,icols]=a[icols,irows]
>>> a
array([[0, 1, 2, 4],
       [1, 0, 3, 5],
       [2, 3, 0, 6],
       [4, 5, 6, 0]])