Re: Strange result in MMa 3.0
- To: mathgroup at smc.vnet.net
- Subject: [mg8153] Re: Strange result in MMa 3.0
- From: tburton at cts.com (Tom Burton)
- Date: Sat, 16 Aug 1997 11:50:57 -0400
- Organization: Brahea Consulting
- Sender: owner-wri-mathgroup at wolfram.com
On 12 Aug 1997 02:11:36 -0400, in comp.soft-sys.math.mathematica you
wrote:
>Dear Group,
>I am used to think, that the definition of NullSpace is:
>NullSpace of linear operator A is a set N(A) defined by all elements x
for
>which A.x=[0]
>
>But Mathematica 3.0 gives me this strange result:
>=========
>In[1]:= A = {{0, 1, 1, 2, -1}, {1, 2, 3, 4, -1},{2, 0, 2, 0, 2}}
>Out[1]= {{0, 1, 1, 2, -1}, {1, 2, 3, 4, -1},{2, 0, 2, 0, 2}}
>
>In[2]:= NullSpace[A]
>Out[2]= {{-1, 1, 0, 0, 1}, {0, -2, 0, 1, 0},{-1, -1, 1, 0, 0}}
>(*this is correct, but transposed and this makes problems later*)
This question comes up often. MMA is perhaps slightly unconventional
here, but not wrong. NullSpace[A] returns a list of row-vectors spanning
the null space. If you want column-vectors, take the transpose.
Tom Burton