Re: Matrix rows
- To: mathgroup at smc.vnet.net
- Subject: [mg65796] Re: Matrix rows
- From: "J Siehler" <jsiehler at gmail.com>
- Date: Mon, 17 Apr 2006 02:28:52 -0400 (EDT)
- References: <e1svao$d0o$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
> If I have a matrix (not square - nearly always has more rows than
> columns). Is there a simple way to check if two (or more) rows are the
> same. I don't need to know how many rows are the same just if any are
> the same. Clearly I could loop through the matrix but this must be of
> order n^2 for an n row matrix.
I don't think you can do better than O(n^2), but you can code it
without looping:
In[1]:=
M1={{1,2,3},{2,5,5},{1,2,3},{2,7,4}};
M2={{1,2,3},{4,5,6},{7,8,9},{10,11,12}};
In[3]:=
DupeQ[m_]:=MatchQ[m,{___,l_,___,l_,___}]
In[4]:=
M1//DupeQ
M2//DupeQ
Out[4]=
True
Out[5]=
False