Thanks Jason!
I see that right_kernel() also works for this.
-- Bill
On Sat, Jun 6, 2009 at 5:41 PM, Jason Grout 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
-~--~~~~--~~--~--~---
