Hello, I am new to non-linear growth modelling in R and I am trying to
reproduce an analysis that was done (successfully) in S-Plus.
I have a simple non-linear growth model, with no nesting. I have attempted
to simplify the call as much as possible (by creating another grouped
object, instead of using subset= and compacting the fixed and random
expressions.)
This is a what the grouped data object looks like:
levelI.data[1:2,]
Grouped Data: GMAE ~ AGE | STUDYID
STUDYID TIME SCORE INCURVES MOST FIRST AGE
19 1005 1 ACTUAL (unaided) in JAMA curves Level I Level I 49.11301
20 1005 2 ACTUAL (unaided) in JAMA curves Level I Level I 56.53745
GMFM GMFCS GMAE YRS
19 91.03394 1 74.16 4.092751
20 95.35018 1 84.05 4.711454
Here is the nlme model:
cp.grad<-deriv(~ (100/(1+exp(-L)))*(1-exp(-exp(logR)*x)), c("L", "logR"),
function(x=0:100,L,logR) NULL)
levelI.nlme<-nlme(GMAE~cp.grad(AGE,limit,lograte),
data=levelI.data,
fixed = limit+lograte~1,
random = limit+lograte~1,
start = c(2.0, -3.0))
I get a subscript out of bounds error - which I am not finding very helpful
because I don't know where things are going wrong.
Bill Shipley posted a similar problem with nlme called with a self-starting
function - but here I don't use a self-starting function and I give the
starting values explicitly so I assume that this is not the same problem he
is having.
What am I doing wrong? Any insights would be very much appreciated.
Kind Regards, Lisa Avery
[[alternative HTML version deleted]]
______________________________________________
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
