Hello David, I thought about this at first as well, e.g.,
x1.lim = quantile(x1,prob=c(0.05,0.95)) y2.lim = quantile(y2,prob=c(0.05,0.95)) x1.sub = x1[ x1 > x1.lim[1] & x1 < x1.lim[2] & y2 > y2.lim[1] & y2 < y2.lim[2]] y2.sub = y2[ x1 > x1.lim[1] & x1 < x1.lim[2] & y2 > y2.lim[1] & y2 < y2.lim[2]] But this is actually does not do what I want because it is not based on the density of the data. What I would like is to keep only the points within an area where the density of points is over x. In other words, if you imagine a contour plot, I'd like to keep all the points within a given contour line. So the data has to be interpolated or smoothed at some point. I am using the kde2d function of the MASS package to plot contour lines but I don't know how to retrieve subsets of what I plot. Also I wouldn't be surprised if there is a trick with quantile that escapes my mind. Thanks for your help, Emmanuel On 19 November 2010 21:25, David Winsemius <dwinsem...@comcast.net> wrote: > > On Nov 19, 2010, at 8:44 PM, Emmanuel Levy wrote: > >> Hello, >> >> This sounds like a problem to which many solutions should exist, but I >> did not manage to find one. >> >> Basically, given a list of datapoints, I'd like to keep those within >> the X% percentile highest density. >> That would be equivalent to retain only points within a given line of >> a contour plot. >> >> Thanks to anybody who could let me know which function I could use! > > What's wrong with quantile? > > -- > David Winsemius, MD > West Hartford, CT > > ______________________________________________ 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.