Message-ID: <5010CE6F.3080402@gmail.com>
Date: 2012-07-26T04:58:23Z
From: Michael Kao
Subject: Remove rows that have repeated items in a particular column
In-Reply-To: <CAC-w7_fQHKFBmienLt6Y1YJwuLU6ekhyxc4eNT7g+Y9QAVuOcg@mail.gmail.com>
Very simple
mat[!duplicated(mat[, 1]), ]
M
On 26/07/12 06:50, Zhongyi Yuan wrote:
> Dear R Users,
>
> I apology for not being able to provide an adequately informative subject.
> Let me describe my problem with an example.
>
> For a matrix
> * (mat <- matrix(c(1,1,2,2,2,3,3, 5,9,1,3,7,4,8), ncol = 2))*
> my desired output is
> * (desired <- matrix(c(1,2,3, 5,1,4), ncol = 2))*
>
> That is, the first column is numerically grouped and only the first item in
> each group is wanted. The second column is in increasing order within each
> group. My actual data will be of size 10^6 by 100 so I am hoping to solve
> this by a simple function. Thank you very much for your help.
>
> Best,
> Zhongyi Yuan
>
> [[alternative HTML version deleted]]
>
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