```
str(Penicillin)
require(lattice)
dotplot(reorder(plate, diameter) ~ diameter, Penicillin, groups = sample,
ylab = "Plate", xlab = "Diameter of growth inhibition zone (mm)",
type = c("p", "a"), auto.key = list(columns = 3, lines = TRUE,
title = "Penicillin sample"))
(fm1 <- lmer(diameter ~ (1|plate) + (1|sample), Penicillin))
L <- getME(fm1, "L")
Matrix::image(L, main = "L",
sub = "Penicillin: Structure of random effects interaction")
```

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