George, Venables & Ripley: Modern Applied Statistics with S, Springer 2002, Chapter 16 (An example: fitting a mixture model) may be helpful.
Hannu Kahra -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of George W. Gilchrist Sent: Thursday, September 16, 2004 5:00 PM To: [EMAIL PROTECTED] Subject: [R] Estimating parameters for a bimodal distribution For several years, I have been using Splus to analyze an ongoing series of datasets that have a bimodal distribution. I have used the following functions, in particular the ms() function, to estimate the parameters: two means, two standard deviations, and one proportion. Here is the code I've been using in S: btmp.bi <- function(vec, p, m1, m2, sd1, sd2) { (exp(p)/(1+exp(p)))*dnorm(vec,mean=m1,sd=abs(sd1))+ (1-(exp(p)/(1+exp(p))))*dnorm(vec,mean=m2,sd=abs(sd2)) } btmp11 <- ms( ~ - sum(log((btmp.bi(btmp1$Temp, p, m1, m2, s1, s2)))), start = list(p = 0.4, m1 = 38, m2 = 40, s1 = 1, s2 = 1), control = list(maxiter = 200)) I have looked in the archives and tried various alternatives, especially optim(), but so far have had nothing but frustration. I've been running this in a semi-automated program on several hundred datasets a few times each month for several years now. I would like to figure out how to move this to R. Thank you for any help you might offer. ================================================================== George W. Gilchrist Email #1: [EMAIL PROTECTED] Department of Biology, Box 8795 Email #2: [EMAIL PROTECTED] College of William & Mary Phone: (757) 221-7751 Williamsburg, VA 23187-8795 Fax: (757) 221-6483 http://gwgilc.people.wm.edu/ ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
