R help - Oct 2012 - nls NAs

Hi- 

I am using the following code: 

start=c(alpha=0.4,beta=0.4) 
warm.10<-nls(warming$umoles60~alpha*exp(beta*warming$T10cm),start
start,data=warming,na.action=na.omit)

This code works for other columns in my dataset that are  similar to $T10cm
but the code does not work for this particular column (T10cm).  I am
assuming this is because warming$T10cm contains NAs.  I have tried just
about everything I can think of to remedy this problem (na.action=na.omit;
na.rm=T; creating a new space such that
warmnoNA<-warming$T10cm!="NA") but
with no success.  With the original code above,  get the following error: 

Error in numericDeriv(form[[3L]], names(ind), env) : 
  Missing value or an infinity produced when evaluating the model 
In addition: Warning message: 
In .swts * (lhs - rhs) : 
  longer object length is not a multiple of shorter object length 

Any ideas? 

Thanks, 

Elizabeth 




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Hello all-

I got some help on this.  While it did not fix the problem with nls, one can
get around the problem by creating a data frame with the NAs excluded.  As
follows:

goodidx<-which(! is.na(warming$T10cm))
warming2<-warming[goodidx,]
warm.10<-nls(umoles60~alpha*exp(beta*T10cm),start = start,data=warming2)

Note there is also a package on on CRAN(nlmrt) that tries to be more
aggressive in finding a
solution to nls type problems. The function wrapnls() in nlmrt runs a
Marquardt code then
nls (same calling sequence, but will not yet handle weights, nor every
possible
expression, though it does most).  

Elizabeth



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