Thanks to all for your help!  That works!

Orange

On Sat, Apr 7, 2012 at 7:25 PM, Gabor Grothendieck
<ggrothendieck@gmail.com>wrote:

> Yes, I had fixed that on my end but didn't notice I had copied the old
> version.  I think its obvious enough that anyone will fix it
> themselves.  Regards.
>
> On Sat, Apr 7, 2012 at 7:23 PM, Rolf Turner <rolf.turner@xtra.co.nz>
> wrote:
> >
> > One other minor glitch I just noticed:
> >
> >    x <- seq_along(x)
> >
> > should read
> >
> >    x <- seq_along(y)
> >
> >    cheers,
> >
> >        Rolf
> >
> >
> > On 08/04/12 10:08, Gabor Grothendieck wrote:
> >>
> >> On Sat, Apr 7, 2012 at 3:58 PM, Gabor Grothendieck
> >> <ggrothendieck@gmail.com>  wrote:
> >>>
> >>> On Fri, Apr 6, 2012 at 9:42 PM, help ly<help.ly2005@gmail.com>  wrote:
> >>>>
> >>>> Dear All,
> >>>>
> >>>> I would like to make a quadratic with a plateau model in R. Is there a
> >>>> package in R doing this? The bentcableAR package seems won't work.
> >>>>
> >>>> The link below describes what I am looking for in R exactly:
> >>>>
> >>>>
> http://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_nlin_sect033.htm
> >>>>
> >>> Use nls directly:
> >>>
> >>> y<- c(0.46, 0.47, 0.57, 0.61, 0.62, 0.68, 0.69, 0.78, 0.7, 0.74,
> >>> 0.77, 0.78, 0.74, 0.8, 0.8, 0.78)
> >>> x<- seq_along(x)
> >>>
> >>> Mean<- function(x, alpha, beta, gamma) {
> >>>   pmin(alpha + beta*x + gamma*x*x, alpha - beta^2/(4 * gamma))
> >>> }
> >>> fm<- nls(y ~ Mean(x, alpha, beta, gamma), start = list(alpha = 0.45,
> >>> beta = 0.05, gamma = -0.0025))
> >>> fm
> >>> summary(fm)
> >>>
> >>> plot(y ~ x)
> >>> lines(fitted(fm) ~ x)
> >>
> >> It was pointed out to me offline that Mean as defined above is not
> >> identical to the definition in the poster's link.  Here is a revision:
> >>
> >> y<- c(0.46, 0.47, 0.57, 0.61, 0.62, 0.68, 0.69, 0.78, 0.7, 0.74,
> >> 0.77, 0.78, 0.74, 0.8, 0.8, 0.78)
> >> x<- seq_along(x)
> >>
> >> Mean<- function(x, alpha, beta, gamma) {
> >>        ifelse(x<  -beta/(2 * gamma), alpha + beta*x + gamma*x*x,
> >>                alpha - beta^2/(4 * gamma))
> >> }
> >> fm<- nls(y ~ Mean(x, alpha, beta, gamma), start = list(alpha = 0.45,
> >> beta = 0.05, gamma = -0.0025))
> >> fm
> >> summary(fm)
> >>
> >> plot(y ~ x)
> >> lines(fitted(fm) ~ x)
> >> with(as.list(coef(fm)), abline(v = -beta/(2 * gamma)))
> >>
> >>
> >
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
>



-- 
Thanks so much!

Orange
help.ly2005@gmail.com

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