Dear all I am struggling with nlme and error message. Even going through Pinheiro, Bates nlme book did not gave me a clue how to avoid this.
fit <- nlme(ce ~ fi1 / ((1+exp(fi2-fi3*tepl))^(1/fi4)), data = temp1na.gr, start = c(fi1=30, fi2=-100, fi3=-.05, fi4=40), fixed = fi1+fi2+fi3+fi4~1, random = pdDiag(fi2+fi4~1), groups = ~spol.f) gives Error in chol((value + t(value))/2) : the leading minor of order 1 is not positive definite Is this error due to lack of experimental points? Here you have one typical part of my data. It is for level spol.f = "3/11". tepl ce 800 28.87 800 29.35 825 29 850 28.73 875 26.83 900 24.07 I have 1-5 points for each level (2 levels with 5 points, 1 level with 4 points, several levels with 2 and 3 points and few with only one point. Fitting this model to each level separately led to several sets of coeficients fi1-fi4 and the separate fits were quite OK. Please give me a hint what can be the cause for this error message and how I shall organize my data to avoid this. (Lack of experimental points is also an answer as I can do some subsequent measurement. R 2.1.0, W 2000, nlme package Best regards Petr Pikal [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
