I'm using the MASS library function confint to extract confidence intervals
from an nls object. In some circumstances (model fit?, shape of
likelihood?) the function confint(nls.fit) returns the following error
message:
Error in profile.nls: Missing value where logical needed: if(abs(.pars[par]
- base)/std.err[par] > 10 * cutoff) break
There's nothing about this in the s-news archive or V&R2 (that I can see).
Does anybody know
1. What this message really means
2. What (if anything) can be done about it or
3. Is there an alternative method? I tried using
sqrt(diag(vcov(nls.fit))), but this produced unsatisfactory results
Kevin Wright, Pioneer Hi-Bred Int'l
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