Re: [R] how to find how many modes in 2 dimensions case Patrick, Here is an example closer to what you are interested in - locating bumps in kernel density estimator.  I am using the example from package KernSmooth, using the function bkde2D(). # Another example for locating maxima in kernel density estimation  data(geyser, package="MASS")  x <- cbind(geyser$duration, geyser$waiting)  est <- bkde2D(x, bandwidth=c(0.7,7))  persp(est$fhat) x <- est$x1 y <- est$x2 z <- est$fhat #  here is a brute-force algorithm to locate ALL the local maxima for (i in 2:(nrow(z)-1) ) { for (j in 2:(ncol(z)-1) ) { lmax <- (z[i,j] > z[i-1,j]) & (z[i,j] > z[i+1,j]) & (z[i,j] > z[i,j-1]) & (z[i,j] > z[i,j+1]) if(lmax) cat("x: ",x[i], "y: ", y[j], "function: ", z[i,j], "\\n") }  } x:  0.724 y:  41.1 function:  2.71e-20  x:  0.858 y:  39.4 function:  1.08e-19  x:  0.992 y:  35.9 function:  2.17e-19  x:  2.07 y:  82.4 function:  0.00795  x:  4.08 y:  77.2 function:  0.00722  x:  4.35 y:  54.9 function:  0.00778 Of these, you can ignore the first 3, which have zero density. Ravi. ---------------------------------------------------------------------------- ------- Ravi Varadhan, Ph.D. Assistant Professor, The Center on Aging and Health Division of Geriatric Medicine and Gerontology  Johns Hopkins University Ph: (410) 502-2619 Fax: (410) 614-9625 Email: rvaradhan@jhmi.edu Webpage:  http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html   ---------------------------------------------------------------------------- -------- -----Original Message----- From: r-help-bounces@stat.math.ethz.ch [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Patrick Wang Sent: Friday, June 08, 2007 3:35 PM To: Bert Gunter Cc: r-help@stat.math.ethz.ch Subject: Re: [R] how to find how many modes in 2 dimensions case Thanks for the reply, maybe I shall say bumps, I can use persp to show a density on a X Y dimensions. one peak is one mode I think. I try to find an automatic way to detect how many peaks of the densities. Pat > Note that "the number of modes" (local maxima??)  is a function of the > bandwidth, so I'm not sure your question is even meaningful. > > Bert Gunter > Genentech Nonclinical Statistics > South San Francisco, CA 94404 > 650-467-7374 > > -----Original Message----- > From: r-help-bounces@stat.math.ethz.ch > [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Patrick Wang > Sent: Friday, June 08, 2007 11:54 AM > To: R-help@stat.math.ethz.ch > Subject: [R] how to find how many modes in 2 dimensions case > > Hi, > > Does anyone know how to count the number of modes in 2 dimensions using > kde2d function? > > Thanks > Pat > > ______________________________________________ > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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@stat.math.ethz.ch 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.