Hello Phil,
In above shown images there are tow equations; upper one is "RSM" (Rating Scale Model ) (from CatR package) and below one is "grsm" model form mirt package.
When I am using CatR package to simulate the RSM parameters for 6 items, I am getting parameter names as lambda and deltas
> library(catR)
> genPolyMatrix(6, 4, model = "RSM")
lambdaj delta1 delta2 delta3
1 -0.626 0.487 0.738 0.576
2 0.184 0.487 0.738 0.576
3 -0.836 0.487 0.738 0.576
4 1.595 0.487 0.738 0.576
5 0.330 0.487 0.738 0.576
6 -0.820 0.487 0.738 0.576
whereas when I use mirt() I get for grsm as I am getting parameters as a1, di's and c
> data(Science)
> mod_grsm=mirt(Science,1,'grsm')
Iteration: 17, Log-Lik: -1621.351, Max-Change: 0.00006
> coef(mod_grsm)
$Comfort
a1 d1 d2 d3 c
par 0.832 4.529 2.201 -1.23 0
$Work
a1 d1 d2 d3 c
par 1.399 4.529 2.201 -1.23 -1.242
$Future
a1 d1 d2 d3 c
par 1.671 4.529 2.201 -1.23 -0.364
$Benefit
a1 d1 d2 d3 c
par 1.498 4.529 2.201 -1.23 -0.894
$GroupPars
MEAN_1 COV_11
par 0 1
How can I relate here these two sets of parameters?
Even the coef(mod_grsm, IRTpars=T) is returning the same output as above.
Thanking you,
Irshad