Dear Danielle, At least in industrial toxicology (my original background) the recent tendency has been to use benchmark dose (BSD) approach instead of NOEL or NOAEL approach due to various problems with the definition and estimation of NO(A)EL. In R this can be achieved using the packages drc and bmd as already mentioned by Drew Tyre.
Here's a short code example that gives you the BMD at 1% level: library(drc) library(bmd) data(daphnids) d24<-daphnids[daphnids$time=="24h",] fit <- drm(no/total~dose, weights = total, data = d24, fct = LL.2(), type = "binomial") ED(fit, 1) bmd(FIT, 0.01) See the following documents for more information, if you're interested in using BSD instead of NO(A)EL: http://www.cdpr.ca.gov/docs/risk/bmdquant.pdf http://www.efsa.europa.eu/en/efsajournal/doc/1150.pdf Jarno ______________________________________________ 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.
