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Matrix with negative indices

asked 2022-07-25 15:15:11 +0100

jesuslop gravatar image

Is there a way or hack to operate with matrices with negative indices? For example a 3x3 matrix with row indices {-1,0,1} and column indices {-1, 0, 1}. So one can do m[-1,-1] for first row and column entry, while still retain matrix operations (ring ops, determinant, etc.). I'm dealing with random walks where the symetry needs that.

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answered 2022-07-25 15:27:43 +0100

slelievre gravatar image

Python uses negative indices to index from the end.

So for a 3 by 3 matrix, you can think of the indices as 0, 1, 2 or equivalently -3, -2, -1.

In other words you could also think of them as 0, 1, -1.

sage: m = matrix(3, [1 .. 9])
sage: m
[1 2 3]
[4 5 6]
[7 8 9]
sage: m[-1, -1]
9
sage: m[-1, 1]
8
sage: m[1, -1]
6
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ok thanks for chiming in fast, but I'd welcome a more direct representation if there's one. The python convention seems to obscure my reasoning about matrices.

jesuslop gravatar imagejesuslop ( 2022-07-25 18:09:15 +0100 )edit

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Asked: 2022-07-25 15:15:11 +0100

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Last updated: Jul 25