[R] Calculating NOEL using R and logistic regression - Toxicology

vito.muggeo
Mon, 02 Apr 2012 23:38:53 -0000

dear Danielle,

The NOEL is a threshold value or breakpoint in the range of dose. Have a look to
the
package segmented to estimate a GLM with unknown breakpoints. The code
(untested) should
be something like

library(segmented)
o<-glm(y~1, family=binomial)
os<-segmented(o, ~dose, psi=starting_psi)

Also the package segmented includes the dataset down that can be useful as an
example..

data(down)
with(down, plot(age, cases/births))

There is a paper of mine on R news 2008 discussing the package..

hope this helps you,
vito



On Mon, 2 Apr 2012 14:45:06 -0800, Danielle Duncan wrote
> Hello, I used the glm function in R to fit a dose-response relationship and
> then have been using dose.p to calculate the LC50, however I would like to
> calculate the NOEL (no observed effect level), ie the lowest dose above
> which responses start occurring. Does anyone know how to do this?
>
> 	[[alternative HTML version deleted]]
>
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