[R] sporadic errors with nlrq() / optim()
Rogers, James A [PGRD Groton]
James_A_Rogers at groton.pfizer.com
Thu May 6 23:04:05 CEST 2004
Dear List,
Apologies if this is a known problem ... I wasn't able to find it on the bug
list, but it is a problem that does not seem to occur with a MAC build of R
2.0, so perhaps this problem has already been addressed for the future.
I am getting *sporadic* errors when refitting the same model to the same
data set, using nlrq() in the nlrq package. The algorithm is not stochastic,
so I would expect to get errors either every time, or never.
###
library(stats) # or library(nls) if using R < 1.9.0
library(nlrq)
test <- data.frame(x = c(7.60090245954208, 6.90775527898214,
6.21460809842219, 5.52146091786225, 4.60517018598809, 3.91202300542815,
3.2188758248682 , 2.52572864430826, 1.83258146374831, 7.60090245954208,
6.90775527898214, 6.21460809842219, 5.52146091786225, 4.60517018598809,
3.91202300542815, 3.2188758248682 , 2.52572864430826, 1.83258146374831,
6.21460809842219, 6.21460809842219),
y = c( 11.0161506644269, 9.84267541313937,
8.66146668057266, 7.48099216286952, 6.50578406012823, 6.24027584517077,
5.63121178182137, 5.71702770140622, 5.64190707093811, 10.8983676287705,
9.91857318995417, 8.74608021735751, 7.58120982619635, 6.361302477573 ,
5.91889385427315, 5.63835466933375 , 5.80211837537706, 5.64897423816121,
8.6195692580331 , 8.70367275835886)
)
i <- 1
while(i < 500) { # I usually hit an error within 50 iterations
cat(i, "\n")
nlrq(y ~ SSfpl(x, A, B, xmid, scal), data = test)
i <- i + 1
}
###
Errors occur with version 1.8.1 and 1.9.0 on both Windows (two different
machines) and UNIX, but not on version 2.0 on a MAC (these are the only R
version - OS permutations I was able to get reports on easily).
Anyone understand what is happening here?
Thanks,
Jim
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