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 -~----------~----~----~----~------~----~------~--~---
