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iter
2011 Dec 19
2
nlrob problem
...list(k=1),data=d,psi=psi.bisquare)
I think the problem is as follows: After the call to nls, a weighted
residual vector is calculated by dividing by sqrt(w). This generates
NaN's for weights of zero, which leads to problems in the subsequent
call to nls during the next iteration:
for (iiter in 1:maxit) {
...
w <- psi(resid/Scale, ...)
...
data$w <- sqrt(w)
...
out <- nls( ....., data=data ....... )
...
resid <- -residuals(out)/sqrt(w) # NaN for w=0
...
}
I wonder whether this pro...