There is no "reversing the dnorm function" -- dnorm is many to one in general (in the normal case, 2 to 1 except for the mean). How would you "reverse" dunif, for example?!
However, with that understanding you could do a simple one dimensional search within the range you want via optimize(), as in > optimize(function(x)abs(dnorm(x) - .3286),lower=-5,upper = 0) ## or use > squared error $minimum [1] -0.6228337 $objective [1] 4.817833e-06 -- Bert On Fri, Nov 12, 2010 at 2:35 PM, Edwin Sun <c...@cfr.msstate.edu> wrote: > > Hello all, > > I have a question about basic statistics. Given a PDF value of 0.328161, > how can I find out the value of -0.625 in R? It is like reversing the dnorm > function but I do not know how to do it in R. > >> pdf.xb <- dnorm(-0.625) > >> pdf.xb > [1] 0.328161 > >> qnorm(pdf.xb) > [1] -0.444997 > >> pnorm(pdf.xb) > [1] 0.628605 > > Many thanks, > > > Edwin > > > -- > View this message in context: > http://r.789695.n4.nabble.com/dnorm-and-qnorm-tp3040427p3040427.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > -- Bert Gunter Genentech Nonclinical Biostatistics ______________________________________________ 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.