[scilab-Users] Strange poly() results

[steven hallacy]

Not sure if it helps, but here's some more information about my setup:

-->[version, opts] = getversion()
 opts  =
 
!ICC  x64  tk  modelicac  atlas  release  Jul 20 2011  11:01:29  !
 version  =
 
 scilab-5.3.3 

Stephen

From: sahallacy at hotmail.com
To: users at lists.scilab.org
Date: Tue, 1 May 2012 17:19:31 -0500
Subject: RE: [scilab-Users] Strange poly() results





Hello,

I'm getting the same results as Kevin.  I am running scilab-5.3.3_x64 on windows 7.

-->clean(coeff(poly(roots(poly([1 1 1],"x","c")),"x","r")))
 ans  =
 
    1. + 0.4330127i    1.    1.  

Stephen

> Date: Tue, 1 May 2012 21:24:48 +0200
> From: serge.steer at inria.fr
> To: users at lists.scilab.org
> Subject: Re: [scilab-Users] Strange poly() results
> 
> PLease can you provide more information (Operating system, Scilab version,...)
> 
> On my Linux box with Scilab-5.3.3  I got
> -->clean(coeff(poly(roots(poly([1 1 1],"x","c")),"x","r"))) 
>  ans  =
>  
>     1.    1.    1.  
>  Serge Steer
> INRIA
> 
> ----- Mail original -----
> > De: "Kevin McCoy" <kevinm at aavatech.com>
> > À: users at lists.scilab.org
> > Envoyé: Lundi 30 Avril 2012 16:39:24
> > Objet: [scilab-Users] Strange poly() results
> > When I run the following:
> > 
> > clean(coeff(poly(roots(poly([1 1 1],"x","c")),"x","r"))) I get ...
> > 
> > ans =
> > 
> > 1. + 0.4330127i 1. 1.
> > 
> > But I'm expecting ...
> > 
> > ans =
> > 
> > 1. 1. 1.
> > 
> > Am I doing something wrong? The documentation says that roots() and
> > poly()
> > are inverse functions, that is, if I construct a polynomial (using
> > poly(pr,"x","r"), where pr are the roots of a polynomial), then I
> > should get
> > back that original polynomial.
> > 
> > Here are some other outputs:
> > 
> > clean(coeff(poly(roots(poly([1 1],"x","c")),"x","r"))) --> 1. 1.
> > [correct]
> > 
> > clean(coeff(poly(roots(poly([1 0 1],"x","c")),"x","r"))) --> 1. 0. 1.
> > [correct]
> > 
> > clean(coeff(poly(roots(poly([1 0 0 1],"x","c")),"x","r"))) --> 0.625 +
> > 0.2165064i 0.4330127i 0 1. [incorrect]
> > 
> > clean(coeff(poly(roots(poly([1 1 2],"x","c")),"x","r"))) --> 0.5 +
> > 0.1653595i 0.5 1. [incorrect]
> > 
> > What am I doing wrong?
> > 
> > Thanks!
> > 
> > 
> > 
> > 
> > 
> > --
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