[R] Probable spammer Re: Problems with nls

[David Winsemius]

It appears to me that rahul143 is a spammer who has automatated  
extraction of old posts to Nabble as a way of delivering  
advertisements. This is an exact copy of a posting to Nabble on

> Mar 28, 2011; 2:33pm  Worik StantonSullivan, Timmerman and White  
> 1999: TA rules, and R
> [Apologies if I have sent this multiple times.  I have been struggling
> with SMTP sewrvers and I have not seen my message appear on the list]
>
> Friends
>
> I am trying to save myself some tedious work.
>
> I am processing a paper from  "The Journal Of Finance * Vol. LIV,  
> No. 5
> October 1999" by Sullivan,  Timmerman and  White.  "Data-Snooping,
> Technical Trading Rule Performance, and the Bootstrap"


This is not the only instance of his postings being identical to old  
questions.

Here is another (and I suspect with diligent search all of them might  
have been constructed the same way.)
:

> Mar 28, 2011; 2:33pm  Worik StantonSullivan, Timmerman and White  
> 1999: TA rules, and R
> [Apologies if I have sent this multiple times.  I have been struggling
> with SMTP sewrvers and I have not seen my message appear on the list]
>
> Friends
>
> I am trying to save myself some tedious work.
>
> I am processing a paper from  "The Journal Of Finance * Vol. LIV,  
> No. 5
> October 1999" by Sullivan,  Timmerman and  White.  "Data-Snooping,
> Technical Trading Rule Performance, and the Bootstrap"



My advice is to divert his postings to your trash bin until his Nabble  
account can be shut down.

-- 
David.


On Dec 2, 2012, at 7:33 AM, rahul143 wrote:

> I'm trying to fit the Bass Diffusion Model using the nls function in  
> R but
> I'm running into a strange problem. The model has either two or three
> parameters, depending on how it's parameterized, p (coefficient of
> innovation), q (coefficient of immitation), and sometimes m (maximum  
> market
> share). Regardless of how I parameterize the model I get an error  
> saying
> that the step factor has decreased below it's minimum. I have tried
> re-setting the minimum in nls.controls but that doesn't seem to fix  
> the
> problem. Likewise, I have run through a variety of start values in  
> the past
> few days, all to no avail. Looking at the trace output it appears  
> that R
> believes I always have one more parameter than I actually have (i.e.  
> when
> the model is parameterized with p and q R seems to be seeing three
> parameters, when m is also included R seems to be seeing four). My
> experience with nls is limited, can someone explain to me why it's  
> doing
> this? I've included the data set I'm working with (published in  
> Michalakelis
> et al. 2008) and some example code.
>
> ## Assign relevant variables
> adoption <-
> c 
> (167000,273000,531000,938000,2056452,3894103,5932090,7963742,9314687,10469060,11393302,11976340 
> )
> time <- seq(from = 1,to = 12, by = 1)
> ## Models
> Bass.Model <- adoption ~ ((p + q)^2/p) * (exp(-(p + q) * time)/((q /  
> p) *
> exp(-(p + q) * time) + 1)^2)
> ## Starting Parameters
> Bass.Params <- list(p = 0.1, q = 0.1)
> ## Model fitting
>
>
>
> -----
> TO GET MORE DETAILS CLICK HERE
> --
> View this message in context: http://r.789695.n4.nabble.com/Problems-with-nls-tp4651641.html
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>
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Alameda, CA, USA