[scilab-Users] SciLab question dealing with linear algebra / tensor multiplication.

[Mike Page]

Hi Julien,

You can use the matrix( ) function to format the data back as a matrix.  In
your case:

B = matrix (A(1, :, :), ,j, k);

will do what you want I think.

Be careful that you understand the data ordering that Scilab uses when
storing Hypermatrices, or you may get the result permuted in the wrong way.

There is also a useful function permute (), which allows you to "transpose"
hypermatrices.  I'm not sure it's what you need, but check it out anyway.

HTH.

Mike.

  -----Original Message-----
  From: Julien Colmars [mailto:julien.colmars at imelavi.fr]
  Sent: 19 May 2010 18:42
  To: users at lists.scilab.org
  Subject: [scilab-Users] SciLab question dealing with linear algebra /
tensor multiplication.


  Hi,

  I've a SciLab problem dealing with linear algebra / tensor multiplication.

  Let's say I have a matrix A wich size is i * j * k ( is it called a matrix
in SciLab ? a 3rd order tensor ? a table ?...)

  SciLab knows that A(:,:,1) is a matrix, and SciLab is able to multiply it
with another matrix...
  But it is not the case of A(1,:,:) for example.... which seems to be a
table of 2 1x2 vectors. [at least in SciLab 4.2.1]

  I'm looking for an elegant solution to avoid many loops... my calculation
is becoming too slow :

  So these are my questions :

    a.. why it is not implemented in SciLab ? (sorry for this naive
question) Is there a specific reason not to authorize to build a matrix from
table values ?

    b.. How could it be done (call to external C/Fortran routine or specific
linear algebra libraries) ?

    c.. Is it possible to simply make a permutation of two subscript : for
example from A(i,j,k) I want to get B = A(k,j,i) ? This way I could make my
basic multiplications...
  I hope it is clear enough...
  Thank you in advance for your help.



  Julien Colmars

  PhD student,
  Équipe Mécanique de l'Arbre et du Bois
  Laboratoire de Mécanique et Génie Civil
  Adresse :   LMGC - UMR5508
                  Université Montpellier 2
                  CC 048 Place Eugène Bataillon
                  34090 Montpellier, France
  Tel. :         +33 (0)4 67 14 96 42
  Fax. :        +33 (0)4 67 14 47 92
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