Dear R community,
I hope someone is out there who has some insights into the ltm package.
Specifically, I am seeking help for the testEquatingData function which is
part of this package.
Here is an example of my data:
#install.packages("ltm", dependencies = TRUE)
library(ltm)
anchor<- as.data.frame(cbind(c(NA, NA, NA, NA, 1), c(NA, NA, NA, 1, NA),
c(1,1,NA,NA,NA)))
names(anchor) <- c("A1","A2", "A3")
items <- list(as.data.frame(cbind(c(NA, NA, NA, NA, 1), c(NA, NA, NA, 1,
NA), c(1,1,NA,NA,NA)))) #let's assume these are the items that I want to
estimate
datAll <- testEquatingData(items, AnchoringItems = anchor)
Now, after I run the testEquatingData() function, the order of the variables
has been changed to A3, V3, A1, A2, V1, V2, instead of, for example A1, A2,
A3, V1, V2,V3, or V1, V2, V3, A1, A2, A3. Since I am using the constraint
function of the three parameter estimation function [e.g. tpm(datAll,
contraint) I would like Anchor items not to be interspersed with the items
to be estimated (V1, V2, etc). I can arrange the order of my constraint
parameters to match the order of the anchor items, but also including
regular items gets tricky. Of particular concern is that second part of the
datAll list (which can be seen when running datAll). The stars indicate that
an item is an anchoring items. However, Their order does not match the order
of the actual items. I hope this makes sense.
Any help would be appreciated.
Thanks,
Alexander
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