[Scilab-users] ?==?utf-8?q? ?==?utf-8?q? Re : problem with matrix of polynomials

[Antoine Monmayrant]

Hello,

It seems that this value is below %eps==2.2e-16, so I though that once encoded in double the difference between 2e-20 and 0 is too small to be properly taken into account.
Am I missing something?

Antoine


Le Lundi, Mars 09, 2020 15:11 CET, Chin Luh Tan <chinluh.tan at bytecode-asia.com> a écrit:
  initially I thought could it be possible the number is too small (or too large) to be handled  by double?  after trying scaling down the problem, I notice that in Scilab 6.0.2 onwards: --> 2e-20*%ians  =    0.  in Scilab 5.5.2 -->2e-20*%ians  =     2.000D-20i   Could this be the issue? thanks. rgds,CL ---- On Mon, 09 Mar 2020 21:04:12 +0800 Stéphane Mottelet <stephane.mottelet at utc.fr> wrote ---- Maybe an inversion made in state-space could me more reliable ?

S.

Le 09/03/2020 à 13:36, sgougeon at free.fr a écrit :
> Hello Federico,
>
> cond() and rcond() do not accept rationals, but the determinant of A is very close to 0:
> --> det(A)
> ans =
>
> 3.573D-10
> ------------------------
> 0.0000027s² +7.433D-10s³
>
> This likely explains that the inversion is not reliable.
>
> Regards
> Samuel
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--
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

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