Hi,
I am trying to run a multilevel model with time nested in people and
people nested in dyads (3 levels of nesting) by initially running a
series of models to test whether the slope/intercept should be fixed or
random. The problem that I am experiencing appears to arise between the
random intercept, fixed slope equation AND.
(syntax:
rint<-lme(BDIAFTER~BDI+WEEK+CORUMTO, random=~1|DYADID/PARTICIP,
data=new)
summary(rint))
the random slope, random intercept model
(syntax:
rslint<-lme(BDIAFTER~BDI+WEEK+CORUMTO, random=~CORUMTO|DYADID/PARTICIP,
data=new)
summary(rslint))
at which point I obtain the exact same results for each model suggesting
that one of the model is not properly specifying the slope or intercept.
Or, I receive the following error message when I try to run the random
slope/random intercept model.
Error in solve.default(pdMatrix(a, fact = TRUE)) :
system is computationally singular: reciprocal condition number
= 6.77073e-017
(whether I receive an error message or the same results depends on the
specific variables in the model).
It has been suggested that I may need to change the default starting
values in the model because I may be approaching a boundary-is this a
plausible explanation for my difficulties? If so, how do I do this in R
and can you refer me to a source that might highlight what would be
reasonable starting values?
If this does not seem like the problem, any idea what the problem may be
and how I might fix it?
Thank you so much for your assistance,
Christine Calmes
Christine A. Calmes, MA
Dept of Psychology
University at Buffalo: The State University of New York
Park Hall 216
Buffalo, NY 14260
[EMAIL PROTECTED]
(716) 645-3650 x578
[[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.
