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 [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
