[R] inverse prediction and Poisson regression
vincent.philion at irda.qc.ca
Fri Jul 25 14:20:09 CEST 2003
Hello, and thanks for this.
> From "www.r-project.org" -> search -> "R site search" -> "LD50", I found
> "dose.p", described on p. 193, sec. 7.2, of Venables and Ripley (2002) Modern
> Applied Statistics with S, 4th ed. (Springer).
I found the same, but this is for logistic regression I think, not Poisson. This is used to calculate the dose which causes 50% "death". I could do it this way by "pretending" my data is binomial.
i/e Y/Ymax = some value between 0 and 1. I could "pretend" my response data is "dead" or "alive", but I'm not sure this is "proper". but maybe it is? Any hints on this?
Y and Ymax follows a Poisson distribution. Can I just use Y/Ymax, run a logistic regression and go on with my life???
(LD50P100 <- dose.p(fitP100, p=14))
> Dose SE
> p = 14: -2.451018 0.04858572
Wow, you got the dose.p function to work with poisson regression? but under SPlus only? is it giving the right results?
> present insomniac state (3:20 AM in California).
The same for me!!!
I worked on this 2:00AM EDT
thanks and have a nice day, possibly starting with a good coffee!!!
> M. PHILION: Does this provide sufficient information for you to now solve
> your problem?
If this works under R and is giving the right solution, I owe you BIG TIME !
bye for now,
Vincent Philion, M.Sc. agr.
Institut de Recherche et de Développement en Agroenvironnement (IRDA)
3300 Sicotte, St-Hyacinthe
téléphone: 450-778-6522 poste 233
courriel: vincent.philion at irda.qc.ca
Site internet : www.irda.qc.ca
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