On Mon, 06 Apr 2015, Keshav Dhandhania <kshav...@gmail.com> writes: > Hi, > > I know that one can find all occurrences of x in a vector v by doing >> which(x == v). > > However, if I need to do this again and again, where v is remaining the > same, then this is quite inefficient. In my particular case, I need to do > this millions of times, and length(v) = 100 million. > > Does anyone have suggestion on how to go about it? > I know of a package called fmatch that does the above for the match > function. But they don't handle multiple matches. >
Perhaps 'match(x, v)' is what you want? In which 'x' may be a vector of length > 1. In any case, have you actually tried package 'fastmatch'? The function 'fmatch', which that package provides, is very fast for repeated lookups in a table 'v'. -- Enrico Schumann Lucerne, Switzerland http://enricoschumann.net ______________________________________________ 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.
