[R] Attachments to R-help postings (Re: Singular Gradient)

[Martin Maechler]

>>>>> "DB" == Douglas Bates <bates at stat.wisc.edu>
>>>>>     on Wed, 7 Feb 2007 17:24:40 -0600 writes:

    DB> On 2/7/07, This Wiederkehr <this.wiederkehr at gmail.com> wrote:
    >> I tried to fit data with the following function:
    >> 
    >> fit<-nls(y~ Is*(1-exp(-l*x))+Iph,start=list(Is=-2e-5,l=2.3,Iph=-0.3
    >> ),control=list(maxiter=500,minFactor=1/10000,tol=10e-05),trace=TRUE)
    >> But I get only a singular Gradient warning...

    DB> Did you get any trace output at all?  It is not clear if you got the
    DB> singular gradient warning before the first iteration completed, which
    DB> means there is a problem at the starting estimates, or after a few
    DB> iterations.  Without the data it is difficult to decide.

    >> the data can by found attached(there are two sampels of data col 1/2 and
    >> 3/4).

    DB> Thanks for offering to include the data.  My copy of your message did
    DB> not have the data enclosed.  Did you perhaps forget to attach the
    DB> file?

More probably he did not attach them with mime type "text/plain".
Many e-mail clients nowadays attach everything and notably text
as unspecified binary ("application/octet-stream").
For security (and anti-spam) reasons, such attachments are
eliminated from postings.

I've now slightly modified this content-filtering option for
R-help, such that (I think) such e-mails will be *rejected* instead 
of just the attachment removed -- I'm just trying that now,
attaching a 2 line text file

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Martin





    >> I tried to fix it by chanching the start parameters but that didn't solve
    >> the problem.

    >> Would it be a possibiliti to use the selfstart Model? How?

    DB> Yes.  Try SSasymp.  I believe that model is equivalent to your model
    DB> but in a different parameterization.