oups I probably did something wrong when I tested it ...
Thanks Paul ----- Mail d'origine ----- De: Pierre-Aimé Agnel <[email protected]> À: [email protected] Envoyé: Wed, 17 Jun 2015 09:28:38 +0200 (CEST) Objet: Re: [Scilab-users] Re : Re: opposite to 'diag' keyword Hello, diag works both ways: Le 17/06/2015 09:22, [email protected] a écrit : > No > > A basic example: > > -->A = [1 0 0 0 ; 0 6 0 0 ; 0 0 -5 0 ; 0 0 0 31] > A = > > 1. 0. 0. 0. > 0. 6. 0. 0. > 0. 0. - 5. 0. > 0. 0. 0. 31. > > -->B = diag(A) > B = > > 1. > 6. > - 5. > 31. > -->A = [1 0 0 0 ; 0 6 0 0 ; 0 0 -5 0 ; 0 0 0 31] A = 1. 0. 0. 0. 0. 6. 0. 0. 0. 0. - 5. 0. 0. 0. 0. 31. -->B = diag(A) B = 1. 6. - 5. 31. -->C = diag(B) C = 1. 0. 0. 0. 0. 6. 0. 0. 0. 0. - 5. 0. 0. 0. 0. 31. > > how a rebuild A from B .... > > NB: > - the purpose is to find a basic but fast way to build a symmetrical matrix > using the following syntax for example : K = K +Kd + K' > - where K is the triangle upper (or lower) matrix and Kd is the diagonal > - I want to decrease the amount of memory in avoiding to use a (nxn) matrix > > > Paul > > ----- Mail d'origine ----- > De: [email protected] <[email protected]> > À: [email protected] > Envoyé: Wed, 17 Jun 2015 09:14:39 +0200 (CEST) > Objet: Re: [Scilab-users] opposite to 'diag' keyword > > Hello, > > Le 17/06/2015 09:05, [email protected] a écrit : >> The question is quite basic: I'm trying to opposite to 'diag' keyword in >> order to build a diagonal matrix from a vector, but I fail so far ... what >> is the trick? > The diag help says "diagonal including or extracting" > > diag([1 2]) > gives the matrix [1 0;0 2] > Is it the "opposite" you want? > > --Jean-Yves > _______________________________________________ > users mailing list > [email protected] > http://lists.scilab.org/mailman/listinfo/users > > _______________________________________________ > users mailing list > [email protected] > http://lists.scilab.org/mailman/listinfo/users -- Pierre-Aimé Agnel R&D Projects Manager Phone: +33.1.80.77.04.67 Mobile: +33.6.82.49.35.23 ----------------------------------------------------------- Scilab Enterprises 143bis rue Yves Le Coz - 78000 Versailles, France Phone: +33.1.80.77.04.68 http://www.scilab-enterprises.com _______________________________________________ users mailing list [email protected] http://lists.scilab.org/mailman/listinfo/users
