----- Original Message ----- From: "Dimitris Rizopoulos" <[EMAIL PROTECTED]> To: "Eleni Rapsomaniki" <[EMAIL PROTECTED]> Cc: <r-help@stat.math.ethz.ch> Sent: Monday, August 07, 2006 1:18 PM Subject: Re: [R] Finding points with equal probability betweennormaldistributions
> if you want to base it on Normality, then you can use: > > prob <- function(x){ > dnorm((x - 5.2) / 2.1) / 2.1 - dnorm((x - 4.2) / 1.1) / 1.1 > } > > uniroot(prob, c(-3, 3)) > sorry but the above gives you only the one solution, probably you need both: dn <- function(x){ dnorm(x, 5.2, 2.1) - dnorm(x, 4.2, 1.1) } rout1 <- uniroot(dn, c(0, 5))$root rout2 <- uniroot(dn, c(5, 10))$root x <- seq(-3, 14, 0.1) plot(x, dnorm(x, 4.2, 1.1), type = "l", col = "red") lines(x, dnorm(x, 5.2, 2.1), col = "blue") abline(v = c(rout1, rout2)) Best, Dimitris > otherwise if you want to estimate it you can use Uwe's solution. > > > I hope it helps. > > Best, > Dimitris > > ---- > Dimitris Rizopoulos > Ph.D. Student > Biostatistical Centre > School of Public Health > Catholic University of Leuven > > Address: Kapucijnenvoer 35, Leuven, Belgium > Tel: +32/(0)16/336899 > Fax: +32/(0)16/337015 > Web: http://med.kuleuven.be/biostat/ > http://www.student.kuleuven.be/~m0390867/dimitris.htm > > > ----- Original Message ----- > From: "Eleni Rapsomaniki" <[EMAIL PROTECTED]> > To: <r-help@stat.math.ethz.ch> > Sent: Monday, August 07, 2006 12:35 PM > Subject: [R] Finding points with equal probability between > normaldistributions > > >> Dear mailing list, >> >> For two normal distributions, e.g: >> >> r1 =rnorm(20,5.2,2.1) >> r2 =rnorm(20,4.2,1.1) >> plot(density(r2), col="blue") >> lines(density(r1), col="red") >> >> Is there a way in R to compute/estimate the point(s) x where the >> density of the >> two distributions cross (ie where x has equal probability of >> belonging to >> either of the two distributions)? >> >> Many Thanks >> >> Eleni Rapsomaniki >> PhD student >> Birkbeck College, UK >> >> ______________________________________________ >> 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. >> > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > ______________________________________________ > 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. > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm ______________________________________________ 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.