[R] inverse function of SSlogis

[Gabor Grothendieck]

Try this.   More info at http://ryacas.googlecode.com :

> library(Ryacas)
> Asym <- Sym("Asym"); xmid <- Sym("xmid"); scal <- Sym("scal")
> x <- Sym("x"); y <- Sym("y")
> Solve(Asym/(1+exp((xmid-x)/scal))==y, x)
expression(list(x == xmid - log(Asym/y - 1) * scal))


On Mon, Mar 29, 2010 at 7:24 AM, Kay Cichini <Kay.Cichini at uibk.ac.at> wrote:
>
> hello,
>
> is there a more convenient way to get the inverse of SSlogis than
> transforming the function by hand?
>
> thanks,
> kay
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