first thing to do when trying to speed up a function is to see where it is spending its time. take a subset of the data and use Rprof to profile the code. my guess is that a lot of time is taken up in the use of dataframes. see if you can use matrices instead.
Sent from my iPad On Jul 2, 2013, at 13:47, Santiago Guallar <sgual...@yahoo.com> wrote: > Hi, > > I have written a function to assign the values of a certain variable 'wd' > from a dataset to another dataset. Both contain data from the same time > period but differ in the length of their time intervals: 'GPS' has regular > 10-minute intervals whereas 'xact' has irregular intervals. I attached > simplified text versions from write.table. You can also get a dput of 'xact' > in this address: http://www.megafileupload.com/en/file/431569/xact-dput.html). > The original objects are large and the function takes almost one hour to > finish. > Here's the function: > > fxG= function(xact, GPS){ > l <- rep( 'A', nrow(GPS) ) > v <- unique(GPS$Ring) # the process is carried out for several individuals > identified by 'Ring' > for(k in 1:length(v) ){ > I = v[k] > df <- xact[xact$Ring == I,] > for(i in 1:nrow(GPS)){ > if(GPS[i,]$Ring== I){# the code runs along the whole data.frame for each i; > it'd save time to make it stop with the last record of each i instead > u <- df$timepos <= GPS[i,]$timepos > # fill vector l for each interval t from xact <= each interval from GPS (take > the max if there's > 1 interval) > l[i] <- df[max( which(u == TRUE) ),]$wd > } > } > } > return(l)} > > vwd <- fxG(xact, GPS) > > > My question is: how can I speed up (optimize) this function? > > Thank you for your help > ______________________________________________ > 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.
