[R] nls
Douglas Bates
bates at stat.wisc.edu
Wed Feb 19 15:35:03 CET 2003
Komanduru Sai C <sck2348 at cacs.louisiana.edu> writes:
> Hi,
>
> I am using nls library
>
> df <- read.table("data.txt", header=T);
> library(nls);
> fm <- nls(y ~ a*(x+d)^(-b), df, start=list(a=max(df->y,na.rm=T)/2,b=1,d=0));
> coef(fm);
> q();
1) Are you sure you meant max(df->y, na.rm=TRUE) and not
max(df$y, na.rm=TRUE)?
2) To begin you may want to use a data frame without the missing data
df1 = na.omit(df[, 1:2])
3) Use the plinear algorithm and change from b to exp(lb)
fm = nls(y ~ (x+d)^(-exp(lb)), data = df1, start=c(lb = 0, d = 0),
alg = 'plinear', trace = TRUE)
--
Douglas Bates bates at stat.wisc.edu
Statistics Department 608/262-2598
University of Wisconsin - Madison http://www.stat.wisc.edu/~bates/
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