Hello all!
I have a problem to use a biexponential regression model:
I use this code:
n3<-nls(proc~SSbiexp(cls,a,b,c,d),data=bline) and this is the error message:

Error in nls(y ~ cbind(exp(-exp(lrc1) * x), exp(-exp(lrc2) * x)), data =
xy,  :
  singular gradient

My data is like this:

structure(list(proc = c(387.177462830167, 508.090511433077,
321.836817656365,
151.226805860727, 150.885315536942, 86.2895998400175, 56.3215592398958,
39.5044440630984, 25.5703078997907, 7.33494872198676), cls = c(0.25,
0.5, 0.75, 1, 1.5, 2, 2.5, 3, 3.5, 4)), .Names = c("proc", "cls"
), row.names = c("0.25", "0.5", "0.75", "1", "1.5", "2", "2.5",
"3", "3.5", "4"), class = "data.frame")

Thank you!

-- 
---
Catalin-Constantin ROIBU
Lecturer PhD, Forestry engineer
Forestry Faculty of Suceava
Str. Universitatii no. 13, Suceava, 720229, Romania
office phone     +4 0230 52 29 78, ext. 531
mobile phone   +4 0745 53 18 01
                       +4 0766 71 76 58
FAX:                +4 0230 52 16 64
silvic.usv.ro

	[[alternative HTML version deleted]]

