Expand terms with '||' notation into separate '|' terms
From the right hand side of a formula for a mixed-effects model, expand terms with the double vertical bar operator into separate, independent random effect terms.
expandDoubleVerts(term)
term |
a mixed-model formula |
the modified term
Because || works at the level of formula parsing, it
has no way of knowing whether a variable is a factor. It
just takes the terms within a random-effects term and literally splits them
into the intercept and separate no-intercept terms,
e.g. (1+x+y|f) would be split into (1|f) + (0+x|f) + (0+y|f).
However, || will fail to break up factors into separate terms;
the dummy function can be useful in this case, although
it is not as convenient as ||.
m <- ~ x + (x || g)
expandDoubleVerts(m)
set.seed(101)
dd <- expand.grid(f=factor(letters[1:3]),g=factor(1:200),rep=1:3)
dd$y <- simulate(~f + (1|g) + (0+dummy(f,"b")|g) + (0+dummy(f,"c")|g),
newdata=dd,
newparams=list(beta=rep(0,3),
theta=c(1,2,1),
sigma=1),
family=gaussian)[[1]]
m1 <- lmer(y~f+(f|g),data=dd)
VarCorr(m1)
m2 <- lmer(y~f+(1|g) + (0+dummy(f,"b")|g) + (0+dummy(f,"c")|g),
data=dd)
VarCorr(m2)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.