Le 30/08/2018 à 09:32, philippe a écrit :
Hi
before scilab6 there was some ambiguity between 1/B=1./B=(1.)/B since
1. = 1 for floating point real numbers. We can see that this problem is
solved now :
--> B=1:3
B =
1. 2. 3.
--> 1./B
ans =
1. 0.5 0.3333333
--> 1/B
ans =
0.0714286
0.1428571
0.2142857
but in the help page it is written that "X=A/B is the solution of X*B=A"
this false for A=1 and B=1:3 as you can see :
--> B*(1/B) // =1 !!!!
ans =
1.
--> (1/B)*B // should be 1 ?
ans =
0.0714286 0.1428571 0.2142857
0.1428571 0.2857143 0.4285714
0.2142857 0.4285714 0.6428571
but this is true for general matrix
--> A=[1 2 ; 3 4]
A =
1. 2.
3. 4.
--> B=[4 5 ; 6 7]
B =
4. 5.
6. 7.
--> B*(A/B) // sould be A ?
ans =
17.5 -8.5
25.5 -12.5
--> (A/B)*B // =A
ans =
1. 2.
3. 4.
this looks confusing ?
No.
For square A, B, invertible B, "A/B" means "A*inv(B)", hence
B*(A/B)=B*A*inv(B) cannot be equal to A (matrix product is not commutative)
S.
Best regards,
Philippe
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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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