# [R-sig-ME] data layout for crossed factors w/interaction in linear mix models

Rafael Diaz tuteson at yahoo.com
Fri Aug 21 21:22:49 CEST 2009

```Dear All,

I am trying to fit a simple linear mixed model (see below
this paragraph) arising from a crossed factorial design with
2 factors and ubalanced number of replicates (from two to
five) in each cell, but I keep getting an error message (see
bottom of message).  The model is:

yijk = intercept + ai + bj + abij + ejik, where:

"intercept" is fixed, and the crosss factors, ai, i =
1,..,10, and bj, j= 1,..,10, are random.  I am
interested in estimating the variance components of these
factors AND their interaction.  I have tried:

fm1 <- lmer(formula = V1~1 + (1|V2) + (1|V3) + (1|V4),
data = 'datos') using two types of data layout for "datos":

1) using a matrix with 3 columns:

y     intercept   ai's  bj's  abij's
y111  1           1     1     1 (1x1)
y112  1           1     1     "
y121  1           1     2     2 (1x2)
y122  1           1     2     "
y123  1           1     2     "
y131  1           1     3     3 (1x3)
.     .           .     .     .
.     .           .     .     .

2) using the design matrix from  Y = XBeta +Zb.
That is, using the same first two columns as above, but
substituting 1020 columns (10 for ai's, 10 for bj's and 100
for abij's) for the last three columns.

I get the message: "Error in eval(predvars, data, env) :
invalid envir argument"

Is my data layout mispecified? Do I need to input initial
values for the random components in order to get the REML
estimates?  I lmer valid for unbalanced designs?  Any help would be greatly appreciated.

Rafael Diaz
California State University Sacramento
Math and Stats

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