Dear list,

I understand that to raise matrix A to power (-1/2) we should use something
like this:

eigen(A)$vectors%*%diag(1/sqrt(eigen(A)$values))%*%t(eigen(A)$vectors)

[from previous discussions:
http://r.789695.n4.nabble.com/matrix-power-td900335.html]

But this will only do it for negative sqrt of the matrix not for other
fraction powers like (-3/2).
Seeing that these things be can done seamlessly in Matlab, I am wondering
if I am missing something in R.

Examples in Matlab:

A =
     1     1     1
     1     2     3
     1     3     6

 A^(-1/2 )=
    1.5099   -0.8262    0.1937
   -0.8262    1.9586   -0.6937
    0.1937   -0.6937    0.6937


 A^(-3/2)=
    7.2020   -9.0481    3.3560
   -9.0481   13.6591   -5.4371
    3.3560   -5.4371    2.2749

Thank you in advance.




-- 
Ebrahim Jahanshiri

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