Removed duplicate parameters of lavaan models with equality constraints from plot.semtree

[manuelarnold]

Previously, plot.semtree showed duplicate parameters when used with lavaan models that include equality constraints. This patch removes those duplicates.

[manuelarnold]

Here is a minimal example. The parameter rvar should appear three times in the plot, and this patch fixes that.

`
library(lavaan)
library(semtree)

d <- HolzingerSwineford1939
d$sex <- factor(d$sex)
d <- d[complete.cases(d), ]

m <- '
f =~ 1x1 + l2x2 + l3*x3

f ~~ f
x1 ~~ rvarx1
x2 ~~ rvarx2
x3 ~~ rvar*x3

f ~ 0*1
x1 ~ 1
x2 ~ 1
x3 ~ 1
'

fit <- lavaan(model = m, data = d)

predictors <- c("sex")

ctrl <- semtree_control(method = "score")

tree <- semtree(model = fit, data = d, predictors = predictors, control = ctrl)

plot(tree)
`

[brandmaier]

Thanks @manuelarnold , this is great!

[brandmaier]

Also, for future PRs, please run a package check first to see whether the changes break CRAN-compatibility. I fixed the "lavaan:::coef" part to "lavaan::coef" because it created a warning.