I'm trying to specify a model using lmer with a binary response and
interaction term, but I get an error I can't parse (see below).

Here is some sample data:

Subject   Concord   Age   Disc
SVC999MX148SU-F   yes   u   int
TOU999JU030S1   yes   u   int
TOU999JU030S1   yes   u   int
TOU999JU030S1   yes   u   int
TUT578MX037S2   yes   g   int
COL140MX114S2   yes   yf   mix
COL140MX114S6   yes   u   mix
COL140MX114S2   yes   yf   mix
COL425MX075S2   yes   of   mix
COL425MX075S2   yes   of   mix
COL425MX075S2   yes   of   mix
STP560JG118S14   no   g   pnl
STP560JG118S22   no   g   pnl
STP560JG118S20   no   g   pnl
STP560JG118S15   no   g   pnl
STP560JG118S20   no   g   int

And here is the model:

lmer_int_ageXdisc <- lmer(Concord ~ Age*Disc
  + (1|Subject), family="binomial", data=d, method="Laplace")

In the actual data set the AgexDisc interaction should have 16 levels.

This produces the error:

Error in devLaplace(PQLpars) : Leading minor of order 7 in downdated X'X is
not positive definite

What does this mean? This error is not thrown for other interactions I
specify from my data.

Here is my session info:

R version 2.4.1 (2006-12-18)
i386-pc-mingw32

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] "stats"   "graphics" "grDevices" "utils"   "datasets" "methods"
[7] "base"

other attached packages:
    lme4    Matrix   lattice
"0.9975-13" "0.9975-11"  "0.14-17"

Thanks in advance for your help!
--
Brian Riordan
NICHD Postdoctoral Fellow
Psychological and Brain Sciences
Indiana University

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