[Scilab-users] Re : problem with matrix of polynomials

[Chin Luh Tan]

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*%i 

ans  =



   0. 



in Scilab 5.5.2



-->2e-20*%i 

ans  =



    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, mailto: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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