如何在numpy中将矩阵变成对角矩阵?
问题描述：
给定矩阵:
x = matrix([[ 0.9, 0.14], [ 0.15, 0.8]])
如何将第一列x[:,0]变成numpy中的对角矩阵?得到:
how can you make the first column, x[:,0], into a diagonal matrix in numpy? to get:
matrix([[0.9, 0],
[0, 0.15]])
答
numpy.diag( x.A[ :, 0 ] )
应该这样做.
matrix和array之间的区别在这里至关重要.仅numpy.diag( x[ :, 0 ] )不会获得相同的结果.当x是matrix时，x.A是numpy.asarray( x )的简写.
The difference between a matrix and an array is crucial here. You won't get the same result from just numpy.diag( x[ :, 0 ] ). x.A is a shorthand for numpy.asarray( x ) when x is a matrix.
因此，出于同样的原因，我想确切地回答您的问题，我想我不应该忘记将答案从array转换回matrix:
So by the same token, to answer your question precisely I guess I shouldn't forget convert the answer from an array back to a matrix:
numpy.matrix( numpy.diag( x.A[ :, 0 ] ) )