Thanks Jason! I see that right_kernel() also works for this.
-- Bill On Sat, Jun 6, 2009 at 5:41 PM, Jason Grout<jason-s...@creativetrax.com> wrote: > > William Cauchois wrote: >> Hi, >> >> I needed to check the null space of the following matrix: >> >> [ -2 7 ] >> [ 0 0 ] >> >> So I typed: >> >> sage: matrix([[-2, 7], [0, 0]]).kernel() >> >> And Sage 4.0.rc0 told me that the basis for the resultant vector space >> was [0, 1]. But this does not seem correct -- [0, 1] does not even >> satisfy the equation -2x_1 + 7x_2 = 0 that we can read off of the >> matrix above (if we augment it with [0, 0] in our head). >> >> So what's wrong? Is kernel() the right method to use for this? Or did >> I read the result incorrectly? Or is my reasoning wrong (the >> possibility that I fear most, since I have a linear algebra final on >> Monday :D)? > > > Sage returns the *left* nullspace, i.e., the solution to the equation > xA=0. You want the right nullspace; so do matrix(...).transpose().kernel(). > > 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 -~----------~----~----~----~------~----~------~--~---
