[Scilab-users] Evaluating a polynomial on a square matrix

[Stéphane Mottelet]

Why just not writing Horner's algorithm directly ?

functionout=horner_mat(p, 
X)a=coeff(p)out=zeros(X);fork=degree(p):-1:0out=out*X+a(k+1)*eye()endendfunction--> 
a=[1 2;3 4]a = 1. 2.3. 4.--> horner_mat(1+%s-%s^2,a)ans =-5. -8. -12. 
-17.--> eye() + a - a^2ans =-5. -8. -12. -17.S.

Le 24/09/2019 à 10:31, Dang Ngoc Chan, Christophe a écrit :
> Hi,
>
> I've got some time this morning (-: so this one seems to work and should be a bit more efficient:
>
> // **********
>
> P = %s^2 + 2*%s + 3
>
> C = coeff(P)
>
> n = size(C, "c")
>
> if n > 1 then
>
>      stringP = "X1 = x; "
>
>      for i = 3:n
>
>          stringP = stringP+"X"+string(i-1)+" = X"+string(i-2)+"*x; "
>
>      end
>
> else
>
>      stringP = ""
>
> end
>
> stringP = stringP+"Y = "+string(C(1))
>
> for i = 2:n
>
>      stringP = stringP+" + "+string(C(i))+"*X"+string(i-1)
>
> end
>
> deff("[Y] = fctP(x)", stringP)
>
> // **********
>
> Regards
>
> --
> Christophe Dang Ngoc Chan
> Mechanical calculation engineer
>
>
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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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