       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:=
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:=
DupeQ[m_]:=MatchQ[m,{___,l_,___,l_,___}]

In:=
M1//DupeQ
M2//DupeQ

Out=
True

Out=
False

```

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