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Re: matrix log and exp [message #30290 is a reply to message #30289]

Wed, 17 April 2002 14:34

hradilv.nospam
Messages: 19
Registered: November 2001

Junior Member

On Wed, 17 Apr 2002 15:32:42 -0400, Paul Van Delst
<paul.vandelst@noaa.gov> wrote:

> G Karas wrote:
>>
>> Hi group,
>> one quickie and possibly difficult:
>>
>> IDL does not have a matrix logarithm logm and matrix
>> exponent expm function. I was thinking of calling lapack
>> routines which do it, but have no experience with lapack
>> or FORTRAN. Anyone with any tips on this one?
>
> Yes. Use ALOG() and EXP().
>
> paulv
>
> --
> Paul van Delst Religious and cultural
> CIMSS @ NOAA/NCEP purity is a fundamentalist
> Ph: (301)763-8000 x7274 fantasy
> Fax:(301)763-8545 V.S.Naipaul

I think what the original post-er is looking for is:

exp(A) = SUM{ (1/n!) * A^n } from 0 to infinity

The only (other) advice I can give is to truncate the sum at some
"reasonable" value (10?, 100?). 'couse you still have to deal with
the A^n part %^{

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[Message index]

		Re: matrix log and exp By: G Karas on Thu, 18 April 2002 06:19
		Re: matrix log and exp By: Paul Van Delst[1] on Thu, 18 April 2002 05:43
		Re: matrix log and exp By: James Kuyper on Wed, 17 April 2002 14:52
		Re: matrix log and exp By: hradilv.nospam on Wed, 17 April 2002 14:34
		Re: matrix log and exp By: Paul Van Delst[1] on Wed, 17 April 2002 12:32

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