Dear R Users,
I want to fit GLMM with lmer with binomial data and a one-way random
effects model with an overall mean and random effects. From R help,
Laplace is slower than PQL, but more accurate. When I fit my model with
Laplace method with
control = list (usePQL = FALSE)),
for most data sets it works well, but for some I get an error message
(Error in if (any(sd < 0)) return("'sd' slot has negative entries") :
missing value where TRUE/FALSE needed)
In these cases I get an estimate for the fixed effect but do not get an
estimate for se.fixef. If I change the method to PQL or change
control = list (usePQL = TRUE)
then I get estimates for both fixed effect and se.fixef, but in the
example below the estimates of fixed effects are different for 3 of 4
cases. Could someone please help me? Which, if any, of the estimates for
the intercept is the best one? And why are they different?
I think the error occurs because the MLE for the between group variance
is zero and somehow the estimate becomes negative. I appreciate any
help.
Thanks,
Emine
install.packages("nlme")
install.packages("Matrix")
install.packages("lme4")
install.packages("car")
library(nlme)
library(Matrix)
library(lme4)
library(car)
library(arm)
y <- c(14, 9, 19, 12, 10, 12, 8, 11, 15, 4, 14, 13, 8, 3)
n <- c( 20, 20, 20, 20, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18)
center <- seq(1:14)
example1 <- lmer(cbind( y, n - y) ~ 1 + ( 1 | center) ,
family = binomial, niter = 50, method = "Laplace", control = list
(usePQL = FALSE))
fixef(example1)
se.fixef(example1)
example2 <- lmer(cbind( y, n - y) ~ 1 + ( 1 | center) ,
family = binomial, niter = 50, method = "Laplace", control = list
(usePQL = TRUE))
fixef(example2)
se.fixef(example2)
example3 <- lmer(cbind( y, n - y) ~ 1 + ( 1 | center) ,
family = binomial, niter = 50, method = "PQL",control = list (usePQL =
TRUE))
fixef(example3)
se.fixef(example3)
example4 <- lmer(cbind( y, n - y) ~ 1 + ( 1 | center) ,
family = binomial, niter = 50, method = "PQL",control = list (usePQL =
FALSE))
fixef(example4)
se.fixef(example4)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Emine Ozgur BAYMAN
PhD Student
Department of Biostatistics,
College of Public Health,
University of Iowa
Office: 2400D UCC, Iowa City / IA
Office Phone: (319) 384 27 52
e-mail: [EMAIL PROTECTED]
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