Displaying 1 result from an estimated 1 matches for "grow_det".
2008 Feb 25
0
logLik calculation in gls (nlme)
...tp://www.zoo.ufl.edu/bolker/splinelik.Rnw
(or http://www.zoo.ufl.edu/bolker/splinelik.pdf ).
Apologies for boneheadedness, but I have taken this as
far as I can for now ...
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## simulate "data" (exponential decrease w/ heterosced.)
set.seed(1001)
n=1000
x = sort(runif(n))
grow_det = exp(-2*x)
grow_var = 0.1*grow_det^2
y = rnorm(n,mean=grow_det,sd=sqrt(grow_var))
dat = data.frame(x=x,y=y) ## nlme likes to have data= specified
## fit true model
library(nlme)
g1 = gnls(y~a*exp(-b*x),
start=list(a=1,b=2),
weights=varPower(form=~fitted(.)),
data=dat)
expdev = -2*logLik(...