[R] matrix exponential: M^0
Duncan Murdoch
dmurdoch at pair.com
Tue Jan 20 17:37:14 CET 2004
On 20 Jan 2004 16:40:07 +0000, Federico Calboli <f.calboli at ucl.ac.uk>
wrote :
>Dear All,
>
>I would like to ask why the zeroeth power of a matrix gives me a matrix
>of ones rather than the identity matrix:
R doesn't have a power operator that knows it's working on a matrix.
M^x raises each entry of M to the power x, it doesn't raise the matrix
to that power. E.g.
> x
[,1] [,2]
[1,] 2 2
[2,] 2 2
> x^2
[,1] [,2]
[1,] 4 4
[2,] 4 4
> x %*% x
[,1] [,2]
[1,] 8 8
[2,] 8 8
It's a little funny that 0^0 gives 1, but that's a reasonable
convention, often useful in likelihood calculations.
Duncan Murdoch
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