Ah of course. Thank you both for your help. Christophe
On Mar 25, 4:00 pm, Jason Grout <jason-s...@creativetrax.com> wrote: > Johan Oudinet wrote: > > On Wed, Mar 25, 2009 at 11:39 AM, Christophe Oosterlynck > > <tif...@gmail.com> wrote: > >> Any comments on this? > > >> it's really strange that when getting a vector from the matrix a > > >>>> b = a[:,0] > >>> you have to use an extra index when you want to select an element from > >> that vector b: > > >>>> b[0][0] > >> instead of just b[0] (this gives a list with 1 element...) > > > No it's not. `b' is also a matrix. So if you just give one argument, > > you get a list of elements: > > a[0] > > (1,0) > > a[0,0] > > 1 > > > b[0] > > (1) > > b[0,0] > > 1 > > Yep, that's right. The b[something,something] notation will always > return a submatrix (not a vector). Use b[something] to get a specific > row as a vector, or use b.row(i) or b.column(i) to get a vector of a > specific row or column. > > sage: a=random_matrix(ZZ,3); a > [-8 -1 -3] > [-1 0 0] > [-1 2 -1] > sage: a.column(0) > (-8, -1, -1) > sage: type(a.column(0)) > <type 'sage.modules.vector_integer_dense.Vector_integer_dense'> > > Jason --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
