Displaying 1 result from an estimated 1 matches for "bricemod".
2011 Jun 30
1
Error "singular gradient matrix at initial parameter estimates" in nls
...parameter estimates
Calls: nls -> switch -> nlsModel
I might be missing something with regard to the different algorithms or
I just have to try again with some different start values. If anyone
finds some time to have a look at that, any advice would be very much
appreciated.
##Brice-Model
bricemod<-nls(log10(D) ~ log10(Do)*exp(((-4*pi*En*Na)*((ro/2)*(r-ro)^2
+(1/3)*(r-ro)^3))/(R*T)), start=list(Do=0.8, En=390,
ro=1.03),trace=TRUE)
Na<-6.0221415*10^23 # Avrogadro's number
T<-1010 # Temp in K
R<-8.3144 #Gas constant [J mol^-1 K^-1]
r<-data.matrix(PRr[c("r")])...