Thanks a lot - that gives the same result as the idea I had - only much easier.
Rainer On Jan 16, 2008 12:18 PM, Dimitris Rizopoulos < [EMAIL PROTECTED]> wrote: > I think you need: > > dx2 <- exp(dx) > dp2 <- dp / dx2 > sum(c(0, diff(dx2)) * dp2) > > > 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<http://www.student.kuleuven.be/%7Em0390867/dimitris.htm> > > > > ----- Original Message ----- > From: "Rainer M Krug" <[EMAIL PROTECTED]> > To: "r-help" <[EMAIL PROTECTED]> > Sent: Wednesday, January 16, 2008 10:34 AM > Subject: [R] Question concerning pdfs > > > > Hi > > > > I have a dataset of absolute growth rates g ranging from close to 0 > > to > > around whatever of which I want to calculate a pdf. > > If I use density(g) the pdf will extend to below 0 so I logtransform > > g > > and do d <- density(log(g)). > > Now I would like to transform this pdf back, i.e. d$x <- > > exp(d$x) but what do I have to do with d$y? > > > > (below is a small example) > > > > Thanks for your help, > > > > Rainer > > > > > > g <- exp(rnorm(100)) ## Just to generate the example data > > > > d <- density(log(g)) > > dx <- d$x > > dp <- d$y > > > > sum(c(0, (diff(dx))) * dp) ## this is equal to one > > plot(dx, dp) > > > > dx2 <- exp(dx) > > dp2 <- ??????? ## what should I do here? > > > > plot(dx2, dp2) ## what should I do here? > > sum(c(0, (diff(exp(dx2)))) * dp2) ## this should be one > > > > > > sum( c(0, (diff(dx2))) * ( dp1 / c(1, (diff(exp(dx2)))) * c(0, > > (diff(dx1)))) ) ##This is obviously also one, but can > > I > > use this to define my dp2? i.e. > > > > dp2 <- dp1 / c(1, (diff(exp(dx2)))) * c(0, (diff(dx1)))) ###???? > > > > ______________________________________________ > > 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. > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > [[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.
