Hi, Suppose the dataset had odd number of columns: set.seed(6458) data2<- data.frame(x1=rnorm(5),x2=rnorm(5),x3=rnorm(5)) n<- prod(dim(data2)) n #[1] 15 dummy<- rep(F,n/2) dummy[sample(1:(n/2),n*.2)]<-T dummy #[1] TRUE FALSE TRUE FALSE FALSE FALSE TRUE
data2[,c("x2", "x3")][matrix(dummy, nc = 2)] <- NA #Error in `[<-.data.frame`(`*tmp*`, matrix(dummy, nc = 2), value = NA) : # unsupported matrix index in replacement #In addition: Warning message: #In matrix(dummy, nc = 2) : # data length [7] is not a sub-multiple or multiple of the number of rows [4] I might do: n1<- 2*nrow(data2) ##for 2 columns dummy<- rep(FALSE,n1) dummy[sample(1:n1,n1*.2)]<-TRUE data2[,c("x2","x3")][matrix(dummy,nc=2)]<-NA data2 # x1 x2 x3 #1 -0.55899744 0.6622481 -0.3305958 #2 0.12776368 NA NA #3 -1.09734838 0.2069539 -0.6997853 #4 0.75919499 -0.5683809 0.4752002 #5 -0.03063141 -0.7549605 2.6038635 A.K. ________________________________ From: Richard Kwock <richardkw...@gmail.com> To: arun <smartpink...@yahoo.com> Cc: Christopher Desjardins <cddesjard...@gmail.com>; R help <r-help@r-project.org> Sent: Friday, August 16, 2013 5:55 PM Subject: Re: [R] Randomly drop a percent of data from a data.frame Try this: data <- data.frame(x1=rnorm(5),x2=rnorm(5),x3=rnorm(5),x4=rnorm(5)) data <- round(data,digits=3) #get the total counts n = prod(dim(data)) #set up a dummy array/matrix dummy <- rep(F, n/2) dummy[sample(1:(n/2), n*.2)] <- T # 5x2 dummy matrix with T and F matrix(dummy, nc = 2) #subset the T indices in x3 and x4 and replace with NAs data[,c("x3", "x4")][matrix(dummy, nc = 2)] <- NA data # x1 x2 x3 x4 #1 -1.310 0.659 NA 0.510 #2 -3.003 -0.004 NA NA #3 0.584 0.310 NA -0.087 #4 1.644 -2.792 -0.390 -0.382 #5 -1.791 0.840 1.137 0.820 Richard On Fri, Aug 16, 2013 at 2:34 PM, arun <smartpink...@yahoo.com> wrote: Hi, >May be this helps: >#data1 (changed `data` to `data1`) >set.seed(6245) > data1 <- data.frame(x1=rnorm(5),x2=rnorm(5),x3=rnorm(5),x4=rnorm(5)) > data1<- round(data1,digits=3) > >data2<- data1 > >data1[,3:4]<-lapply(data1[,3:4],function(x){x1<- >match(x,sample(unlist(data1[,3:4]),round(0.8*length(unlist(data1[,3:4])))));x[is.na(x1)]<-NA;x}) > data1 ># x1 x2 x3 x4 >#1 0.482 1.320 NA -0.142 >#2 -0.753 -0.041 -0.063 0.886 >#3 0.028 -0.256 -0.069 0.354 >#4 -0.086 0.475 0.244 0.781 >#5 0.690 -0.181 1.274 1.633 > > >#or >data2[,3:4]<-lapply(data2[,3:4],function(x){x1<- >match(x,sample(unlist(data2[,3:4]),round(0.8*length(unlist(data2[,3:4])))));x[is.na(x1)]<-NA;x}) > data2 ># x1 x2 x3 x4 >#1 0.482 1.320 -0.859 -0.142 >#2 -0.753 -0.041 NA NA >#3 0.028 -0.256 -0.069 0.354 >#4 -0.086 0.475 0.244 0.781 >#5 0.690 -0.181 1.274 1.633 >A.K. > > > > >----- Original Message ----- >From: Christopher Desjardins <cddesjard...@gmail.com> >To: "r-help@r-project.org" <r-help@r-project.org> >Cc: >Sent: Friday, August 16, 2013 3:02 PM >Subject: [R] Randomly drop a percent of data from a data.frame > >Hi, >I have the following data. > >> set.seed(6245) >> data <- data.frame(x1=rnorm(5),x2=rnorm(5),x3=rnorm(5),x4=rnorm(5)) >> round(data,digits=3) > x1 x2 x3 x4 >1 0.482 1.320 -0.859 -0.142 >2 -0.753 -0.041 -0.063 0.886 >3 0.028 -0.256 -0.069 0.354 >4 -0.086 0.475 0.244 0.781 >5 0.690 -0.181 1.274 1.633 > >What I would like to do is drop 20% of the data. But I want this 20% to >only come from dropping data from x3 and x4. It doesn't have to be evenly, >i.e. I don't care to drop 2 from x3 and 2 from x4 or make sure only one >observation has missing data on only one variable. I just want to drop 20% >of the data through x3 and x4 only. In other words, > > x1 x2 x3 x4 >1 0.482 1.320 -0.859 NA >2 -0.753 -0.041 -0.063 0.886 >3 0.028 -0.256 NA 0.354 >4 -0.086 0.475 NA 0.781 >5 0.690 -0.181 NA 1.633 > >OR > > x1 x2 x3 x4 >1 0.482 1.320 NA -0.142 >2 -0.753 -0.041 -0.063 0.886 >3 0.028 -0.256 NA NA >4 -0.086 0.475 0.244 NA >5 0.690 -0.181 1.274 1.633 > >OR > > x1 x2 x3 x4 >1 0.482 1.320 -0.859 -0.142 >2 -0.753 -0.041 -0.063 NA >3 0.028 -0.256 -0.069 NA >4 -0.086 0.475 0.244 NA >5 0.690 -0.181 1.274 NA > >ETC. are all fine. > >Any ideas how I can do this? >Chris > > [[alternative HTML version deleted]] > >______________________________________________ >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. > > >______________________________________________ >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. > ______________________________________________ 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.