Just to add another option to what Arun has provided below. That approach is very generalizable to data frames with >2 columns, where you want to filter based upon a finding a maximum value (or other perhaps more complex criteria) within one or more grouping columns and return all of the columns in the original data frame.
In this special case of a two column data frame, you can use ?aggregate easily with a formula based approach that might be easier to read. aggregate() essentially encapsulates what Arun has done below. Thus: > DF Point_counts Psi_Sp 1 A 0 2 A 1 3 B 1 4 B 2 5 B 0 6 C 1 7 D 1 8 D 2 > aggregate(Psi_Sp ~ Point_counts, data = DF, max) Point_counts Psi_Sp 1 A 1 2 B 2 3 C 1 4 D 2 Regards, Marc Schwartz On Mar 6, 2013, at 8:42 PM, arun <smartpink...@yahoo.com> wrote: > Hi, > > dfrm<- read.table(text=" > Point_counts Psi_Sp > > 1 A 0 > 2 A 1 > 3 B 1 > 4 B 2 > 5 B 0 > 6 C 1 > 7 D 1 > 8 D 2 > ",sep="",header=TRUE,stringsAsFactors=FALSE) > res<-do.call(rbind,lapply(split(dfrm,dfrm$Point_counts),function(x) > x[which.max(x$Psi_Sp),])) > row.names(res)<-1:nrow(res) > # Point_counts Psi_Sp > #1 A 1 > #2 B 2 > #3 C 1 #your input data doesn't have 0 > #4 D 2 > A.K. > > > > ----- Original Message ----- > From: Francisco Carvalho Diniz <chicocdi...@gmail.com> > To: r-help@r-project.org > Cc: > Sent: Wednesday, March 6, 2013 6:21 PM > Subject: [R] Fwd: How to conditionally remove dataframe rows? > > Hi, > > I have a data frame with two columns. I need to remove duplicated rows in > first column, but I need to do it conditionally to values of the second > column. > > Example: > > Point_counts Psi_Sp > > 1 A 0 > 2 A 1 > 3 B 1 > 4 B 2 > 5 B 0 > 6 C 1 > 7 D 1 > 8 D 2 > > > I need to turn this data frame in one without duplicated rows at > point-counts (one visit per point) but maintain the ones with maximum value > at Psi_Sp, e.g. remove row 1 and maintain 2 or remove rows 3 and 5 and > maintain 4. At the end I want a data frame like the one below: > > Point_counts Psi_Sp > > 1 A 1 > 2 B 2 > 3 C 0 > 4 D 2 > > How can I do it? I found several ways to edit data frames, but > unfortunately I cound not use none of them. > > I appreciate > > Francisco ______________________________________________ R-help@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.
