R help - Jan 2005 - Help in customising the NLS function to spit out mean and SD of new fit!!

i'm coding in  R(first time) for a paper my colleague is publishing.
 i plotted a histogram for 6000 values. Taking the mean and sd of the  midpoints
i did a dnorm and got the densities.
 pl<-dnorm(trimmedvals,mean=midsmean,sd=midsSD)
 (now in a loop of 5 times)
 i plotted these experimental values against theoretical values using
 the nls function the following way.
 nlsresult<-nlsModel(pl ~ 1/sqrt(2
*pi)*std)*2.71828^2/(2*std4^2)),data=answer,start=list(std4=std4,sm=sm))
 in the formula mean was mid point of 1st frequency bar and sd was sd  of 6000
values.I do this 5 times each time changing the mean in the formula to be the
mid point of the next frequency bar.
 now i plotted plot(fittedvals ~trimmedvals)
 
I am told to plot experimental vs theoretical vlaues from the  histogram and get
a non linear least square curve fit.
 I need the mean and sd of this new fit to proceed to my next  module.I'm
not sure if i'm on track. Excuse me if this sounds too  naive.If nls is not
what i should be using can you please give me some  pinters to solve this.

 Thanks in advance.

Choudary Jagarlamudi
Instructor
Southwestern Oklahoma State University
STF 254
100 campus Drive
Weatherford OK 73096
Tel 580-774-7136

It **sounds ** like you are trying to fit a nonparametric density to 6000
values...  If so, please stop what you are doing and see ?density. You could
also search on "fit density" or something similar on the R site
search, as
there are other R functions in R packages that do density fitting (ash is
one, but other recommendations anyone?).

If this is not what you are trying to do, I think you are still likely going
about it in the wrong way -- histograms lose information and are notoriously
dependent on the choice of cutpoints (which is part of the motivation for
Scott's ash package). You might wish to consult a local statistician to get
some better approaches to whatever it is that you're trying to do.

Cheers,
Bert Gunter


-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Jagarlamudi, Choudary
Sent: Friday, January 07, 2005 10:50 AM
To: r-help at stat.math.ethz.ch
Subject: [R] Help in customising the NLS function to spit out mean and SD
ofnew fit!!

 i'm coding in  R(first time) for a paper my colleague is publishing.
 i plotted a histogram for 6000 values. Taking the mean and sd of the
midpoints i did a dnorm and got the densities.
 pl<-dnorm(trimmedvals,mean=midsmean,sd=midsSD)
 (now in a loop of 5 times)
 i plotted these experimental values against theoretical values using
 the nls function the following way.
 nlsresult<-nlsModel(pl ~ 1/sqrt(2
*pi)*std)*2.71828^2/(2*std4^2)),data=answer,start=list(std4=std4,sm=sm))
 in the formula mean was mid point of 1st frequency bar and sd was sd  of
6000 values.I do this 5 times each time changing the mean in the formula to
be the mid point of the next frequency bar.
 now i plotted plot(fittedvals ~trimmedvals)
 
I am told to plot experimental vs theoretical vlaues from the  histogram and
get a non linear least square curve fit.
 I need the mean and sd of this new fit to proceed to my next  module.I'm
not sure if i'm on track. Excuse me if this sounds too  naive.If nls is not
what i should be using can you please give me some  pinters to solve this.

 Thanks in advance.

Choudary Jagarlamudi
Instructor
Southwestern Oklahoma State University
STF 254
100 campus Drive
Weatherford OK 73096
Tel 580-774-7136