[R] error message

[gabriela escati peñaloza]

Hello,
we work in nlme, with R version 2.2.1.
We ran the follwing sentence, a growth function,

> formula(my data.gd)
L.gd ~ Largo | ID

 Rich<- function(Largo, Linf, K, t0, m) 
        Linf *(1-exp(-K(edad-t0)))^(1/(1-m))

> Rich.nlme <- nlme(Largo ~ Rich(edad, Linf, K, t0,
m),
+ data = L.gd,
+ fixed = Linf + K +t0 +m~ 1,
+       start = list(fixed = c(800, 0.3,-0.5,0.3)))


And the program gave us this error message,

Error: Singularity in backsolve at level 0, block 1
In addition: Warning messages:
1: NaNs produced in: log(x) 
2: NaNs produced in: log(x)
 
Does anyone know what this means?

We would apreciate if you could point us to a
reference


Lic. Gabriela Escati Peñaloza
Biología y Manejo de Recursos Acuáticos
Centro Nacional Patagónico(CENPAT). 
CONICET
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Argentina

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