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Remove rows that have repeated items in a particular column
5 messages · Zhongyi Yuan, Michael Kao, arun
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]]
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
HI, Try this: ?mat[!duplicated(mat[,1]),] ???? [,1] [,2] [1,]??? 1??? 5 [2,]??? 2??? 1 [3,]??? 3??? 4 A.K. ----- Original Message ----- From: Zhongyi Yuan <zhongyi-yuan at uiowa.edu> To: r-help at r-project.org Cc: Sent: Thursday, July 26, 2012 12:50 AM Subject: [R] Remove rows that have repeated items in a particular column 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]] ______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
HI, One more solution to you: mat1<-data.frame(mat) ?desired<-as.matrix(do.call(rbind,lapply(split(mat1,mat1$X1),function(x) head(x,1)))) ?colnames(desired)<-NULL ?desired ? [,1] [,2] 1??? 1??? 5 2??? 2??? 1 3??? 3??? 4 A.K. ----- Original Message ----- From: Zhongyi Yuan <zhongyi-yuan at uiowa.edu> To: r-help at r-project.org Cc: Sent: Thursday, July 26, 2012 12:50 AM Subject: [R] Remove rows that have repeated items in a particular column 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]] ______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
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