[R] Negative exponential fit

[Peter Ruckdeschel]

Am 29.11.2011 07:06, schrieb Indrajit Sengupta:
> What have you tried so far - can you explain? "fitdistrplus" package is the default package for fitting distributions.
> 
> Regards,
> Indrajit
> 
> 
> 
> ________________________________
>  From: rch4 <rch4 at geneseo.edu>
> To: r-help at r-project.org 
> Sent: Tuesday, November 29, 2011 8:39 AM
> Subject: [R] Negative exponential fit
>  
> We need help....
> 
> We are doing a project for a statistical class in and we are looking at
> world record times in different running events over time. We are trying to
> fit the data with a negative exponential but we just cant seem to get a
> function that works properly. 
> we have on our x-axis the date and on the y-axis the time(in seconds). So as
> you can imagine, the times have decreased and appear to be approaching a
> limit. Any ideas for a nls function that would work for us would be greatly
> appreciated. 
> 
> Rob
> 
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I do not want to shed out any doubt as to the merits of
pkg fitdistrplus, in particular for censored data, but
seconding Uwe's reply later in this thread, you may
also want to check out pkg distrMod on CRAN ---

M. Kohl, P. Ruckdeschel (2010): R Package distrMod: S4
  Classes and Methods for Probability Models. Journal of Statistical
  Software, 35(10), 1-27. URL http://www.jstatsoft.org/v35/i10/.

which offers quite some additional flexibility for model
fitting---including "new models" (built on distributions
which "have no name" but instead are image distributions
under arithmetic transformations of existing ones, see
example M2 in the cited ref) and (nonlinear) transformations
of the parameter (see Example p.15, cited ref).

Best regards,
Peter