On Thu, Oct 8, 2009 at 3:48 PM, Monica Pisica <pisican...@hotmail.com>wrote:
> > > Hi, > > I would like to find out the coordinates of the intersection points of 2 > density curves. I did a search but i didn't get any significant results. I > really hope some of you have some ideas. here it is an example: > > set.seed(123) > x1 <- rnorm(100, 1, 1) > x2 <- rnorm(100, 0, 1) > d1 <- density(x1) > d2 <- density(x2) > > plot(d1, col = 2) > lines(d2, col = 4) > > if you specify n, from ant to in density() and keep them the same, then the density estimates are done for the same x-coordinates. Therefore you can compare d1$y with d2$y to deternine, where they intersect: d2 <- density(x2, from=-3, to=5, n=2048) d1 <- density(x1, from=-3, to=5, n=2048) plot(d1, col = 2) lines(d2, col = 4) d1$y < d2$y intersX <- d1$x[as.logical(abs(diff(d1$y < d2$y)))] intersY <- d1$y[as.logical(abs(diff(d1$y < d2$y)))] abline(v=inters) abline(h=intersY) Cheers, Rainer > Now i would like to know the coordinates of the intersection point. I did > some "trial and error" and i come up with these .... (that means i did > several vertical and horizontal lines through the graph until visually i > "hit" the intersection point) > > abline(v = 0.35, lty = 2) > abline(h = 0.34, lty = 2) > > I really appreciate any hints you may have, thanks so much, > > Monica > _________________________________________________________________ > Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. > http://clk.atdmt.com/GBL/go/171222985/direct/01/ > ______________________________________________ > 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. > -- Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany) Centre of Excellence for Invasion Biology Natural Sciences Building Office Suite 2039 Stellenbosch University Main Campus, Merriman Avenue Stellenbosch South Africa Cell: +27 - (0)83 9479 042 Fax: +27 - (0)86 516 2782 Fax: +49 - (0)721 151 334 888 email: rai...@krugs.de Skype: RMkrug Google: r.m.k...@gmail.com [[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.
