R help - Oct 2011 - how to remove the redundant rows of a matrix

Hi,

I have a matrix like this, two columns: a, b

 a b  c1 21  c2 19  c2 20  c2 20  c4 25  c5 18  c5 18
how to prepare a new matrix removing the rows with repeated units in b
columns, like there are two 20 and two 18 in b column (others are unique in
b col).  I wanna a pure matrix with one 20 and one 18.

Thanks a lot!

Yan

	[[alternative HTML version deleted]]

Your data didn't come through with the html stripping but either
unique() or duplicated() should get you where you need to be.

Michael

On Mon, Oct 31, 2011 at 12:25 PM, yan liu <yanliusun at gmail.com>
wrote:
> Hi,
>
> I have a matrix like this, two columns: a, b
>
> ?a b ?c1 21 ?c2 19 ?c2 20 ?c2 20 ?c4 25 ?c5 18 ?c5 18
> how to prepare a new matrix removing the rows with repeated units in b
> columns, like there are two 20 and two 18 in b column (others are unique in
> b col). ?I wanna a pure matrix with one 20 and one 18.
>
> Thanks a lot!
>
> Yan
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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