Hi, I would have thought that these two constructions would produce the same result but they do not.
Resp <- rbinom(10, 1, 0.5) Stim <- rep(0:1, 5) mm <- model.matrix(~ Stim) Xb <- mm %*% c(0, 1) ifelse(Resp, log(pnorm(Xb)), log(1 - pnorm(Xb))) pnorm(as.vector(Xb), lower.tail = Resp, log.p = TRUE)
ifelse(Resp, log(pnorm(Xb)), log(1 - pnorm(Xb)))
[1] -0.6931472 -1.8410216 -0.6931472 -0.1727538 -0.6931472 [6] -0.1727538 -0.6931472 -1.8410216 -0.6931472 -1.8410216
pnorm(as.vector(Xb), lower.tail = Resp, log.p = TRUE)
[1] -0.6931472 -1.8410216 -0.6931472 -1.8410216 -0.6931472 [6] -1.8410216 -0.6931472 -1.8410216 -0.6931472 -1.8410216 If I have missed something obvious, I would be grateful to have it pointed out.
sessionInfo()
R version 2.10.1 beta (2009-12-04 r50668) i386-apple-darwin9.8.0 locale: [1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods [7] base loaded via a namespace (and not attached): [1] tools_2.10.1 Thanks for any enlightenment. best, Ken -- Ken Knoblauch Inserm U846 Stem-cell and Brain Research Institute Department of Integrative Neurosciences 18 avenue du Doyen Lépine 69500 Bron France tel: +33 (0)4 72 91 34 77 fax: +33 (0)4 72 91 34 61 portable: +33 (0)6 84 10 64 10 http://www.sbri.fr/members/kenneth-knoblauch.html ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel