Displaying 2 results from an estimated 2 matches for "nonidentifi".
2007 Oct 05
1
lme (or lmer) question
Folks:
In the following mixed effect model, the "x" and residual variance
components are nonidentifiable. Yet lme() (or the equivalent in lmer())
happily produces an answer in which the sum of the variance components is
the correct estimate of the single variance parameter. Why? -- i.e. why
doesn't lme complain?
x <- 1:50
y <- rnorm(50)
m1 <- lme( y ~ 1, rand = ~1|x)
Many thanks,...
2011 Feb 28
3
nls not solving
I am running the following nls equation. I tried it with data that excel was
fitting and got the error:
singular gradient matrix at initial parameter estimates
I thought it was due to a low number of points (6), but when I create a
dataset, I get the same problem. If I remove the parameter "a," then it can
find a solution. Does anyone know what I can do to fit this model?