I'm trying to estimate a Confirmatory Multiple Group model with two groups and two latent dimensions. I've done some EFA to establish the pattern of loadings and decided how to assign each item to each of the two factors. I have 30 items in total: the first 6 I want to use as "anchors" since they are the same in the two groups, and the remaining 24 are specific to either group (so they are NA in the other group). My ultimate aim is to assess the level of "skills" in the two groups, and then score the individuals on both dimensions.
model.syntax <- ('
EXT = 1-3, 7-12, 14, 15, 18, 19, 21, 23, 24, 26, 28
INT = 4-6, 13, 16, 17, 20, 22, 25, 27, 29, 30
CONSTRAINB = (1-3, a1), (4-6, a2), (1-6, d), (7-12, 14, 15, 18, 19, 21, 23, 24, 26, 28, a1), (13, 16, 17, 20, 22, 25, 27, 29, 30, a2), (7-30, d)
COV = EXT*INT
')
mod.anch <- multipleGroup(items, model=model.syntax, group=cohort, invariance=c('free_means', 'free_var'), method = 'MHRM')
Everything runs smoothly, but I get an error when I try to plot anything from the model object (I'm particularly interested in having a look at the trace lines):