linkp function

Linkage Plan

Calculates the number of common items between a list of forms.

linkp(mods = NULL, coef = NULL)

Arguments

• mods: an object of the class modIRT containing item parameter coefficients and their covariance matrix of the forms to be equated.
• coef: list of matrices (one for each form) containing item parameter estimates. The names of the rows of each matrix should be the names of the items.

Returns

A matrix whose elements indicate the number of common items between the forms. On the diagonal of the matrix there are the number of items of each form.

Author(s)

Michela Battauz

See Also

est2pl, est3pl, estrasch

Examples

## Not run:

library("mirt")
data("data2pl")

m1 <- mirt(data2pl[[1]], SE = TRUE)
m2 <- mirt(data2pl[[2]], SE = TRUE)
m3 <- mirt(data2pl[[3]], SE = TRUE)
m4 <- mirt(data2pl[[4]], SE = TRUE)
m5 <- mirt(data2pl[[5]], SE = TRUE)

mlist<- list(m1,m2,m3,m4,m5)
test <- paste("test", 1:5, sep = "")
mod2pl <- modIRT(est.mods = mlist, names = test, display = FALSE)
linkp(mod2pl)
## End(Not run)

# ===========================================================================
# the following code uses item parameter estimates previously obtained

data(est3pl)
linkp(coef = est3pl$coef)