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Re: Eigenvalues

• To: mathgroup at smc.vnet.net
• Subject: [mg77771] Re: [mg77699] Eigenvalues
• From: Sseziwa Mukasa <mukasa at jeol.com>
• Date: Sat, 16 Jun 2007 03:33:04 -0400 (EDT)
• References: <200706150832.EAA15805@smc.vnet.net>

On Jun 15, 2007, at 4:32 AM, amitsoni.1984 at gmail.com wrote:

> Hi,
>
> I am using Eigenvalues[S] to find the eigenvalues of a matrix. When S
> is a non singular matrix(size 500X500), the result comes very fast and
> I get numerical values of the eigenvalues. When S is singular, or very
> close to singular, the same command takes a very long time and I get
> the solution in the following form:
> ------------------------------------------
> (Root[1 -
> 6859435996762057045187843293221812393683817376046833008234880515639280 
> 04
> 00 #1 +
> 422683709458129987020719509512322527334828765466847787730553472756576
> 3506258708383447822509137758993927488132783442108014806593541358448555 
> 767500
> #1^2 -
> 4756334945955210795836139142803033950863408883091629073980127621488009
> 9538622776902139577425659266255925123024793120672024133734311577213768 
> 95723657
> 92383917222956224461254901373715676847804396794660504978304000000
> #1^3 +
> 1490439316139768721738053003572341238241771871563766864860921729266477 
> 34083521
> 3178933085853599699167808789742199539196497269955741918549529138824590 
> 23542023
> 1375808689867514677371127 ..........
> -------------------------------------------------------------
>
> How can I get the solution(eigenvalues) as numerical values?

Are all your matrix entries integers?  If so, and if you can work  
with machine precision use N to turn your matrix entries into machine  
precision numbers, this may make the algorithm run faster at the  
expense of precision, or just apply N to the Root objects if you need  
the precision.

Regards,

Ssezi

• References:
  • Eigenvalues
    • From: "amitsoni.1984@gmail.com" <amitsoni.1984@gmail.com>