Hi Anna, I can't think of a simple way, but this function may make you happier:
step_median<-function(x,window) { x<-unlist(x) stop<-length(x)-window+1 xout<-NA nindx<-1 for(i in seq(1,stop,by=window)) { xout[nindx]<-do.call("median",list(x[i:(i+window-1)])) nindx<-nindx+1 } return(xout) } apply(df,1,step_median,3) This should return a matrix where the columns are the medians calculated from blocks of "window" width on each row of "df". As Bert noted, you may want to think about a "rolling" median where the "windows" overlap. This can be done like so: library(zoo) apply(df,1,rollmedian,3) Jim On Fri, Apr 17, 2020 at 12:32 AM aiguo li via R-help <r-help@r-project.org> wrote: > > Hi all, > I need to calculate a row median for every three columns of a dataframe. I > made it work using the following script, but not happy with the script. Is > there a simpler way for doing this? > df = data.frame("a"=c(2,3,4), > "b"=c(3,5,1),"c"=c(1,3,6),"d"=c(7,2,1),"e"=c(2,5,3),"f"=c(4,5,1))tmed <- > function(dt) {x = apply(dt,1,median); return(x)}n =seq(1, ncol(df),3)w=0;for > (i in n) { m=i+2; dt = df[,i:m]; y=tmed(dt); w = cbind(w,y)}t.med <- > w[,2:3] > Thanks, > Anna > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.