Hello all!
I am trying to estimate four parameters (mu, sigma, theta and lambda) of a model
Using the nls package in R, I can only get it to work if I limit the number of
parameters to be estimated to three (i.e. mu, sigma and theta) as in the first
model - mod1 - below. Including a fourth parameter (lambda) like in the second
model - mod2 - returns the following error messages
1. Error in numericDeriv(form[[3L]], names(ind), env):
2. Missing value or an infinity produced when evaluating the model
mod1<-nls(germ~1-(exp(-1*((psi-(theta/time)-mu)/sigma))),start=c(mu=-2.7,
theta=3, sigma=3), data=ht)
mod1
mod2<-nls(germ~1-(exp(-1*((psi-(theta/time)-mu)/sigma)^lambda)),start=c(mu=-2.7,
theta=3, sigma=3, lambda=-1.2), data=ht)
mod2
Please have a look at my code and tell how I might get it to work. A sample of
my data is shown below. It has five levels of psi (0, -0.4, -0.8, -1.2 and
-1.6).
psi
time
germ
0
1.333333
0
0
1.416667
0
0
1.5
0.04
0
1.583333
0.04
0
2.083333
0.08
0
2.166667
0.16
0
2.25
0.24
0
2.583333
0.64
0
2.666667
0.72
0
2.916667
1
.
.
.
-1.6
2.916667
0
-1.6
3.166667
0
-1.6
3.666667
0
-1.6
7.666667
0
-1.6
9.666667
0
-1.6
12.66667
0
-1.6
19.66667
0
Dr Onoriode Coast
Postdoctoral Fellow
Agriculture Flagship
CSIRO
E onoriode.co...@csiro.au T +61 2 6799 1541 M 0477 386 110
21888 Kamilaroi Highway, Narrabri, NSW, 2390 Australia
www.csiro.au
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