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rlogis
2010 Mar 11
2
about IRT simulation
hello R:
we have a two-parameter IRT simulation code. The goal is to generate a
response matrix.But the "for" part doesn't run. we don't know what is wrong
with it.
Thanks so much~~~
I <- 10
J <- 5
response <- matrix(0, 10, 5)
pij <- function(a,b,theta)
{
a <- rnorm(J, 0.8, 0.04)
a
b <- rnorm(J, 0, 1)
b
theta <- rnorm(I, 0,1)
theta
for( i in 1:I ) {
for(
2011 Nov 20
2
ltm: Simplified approach to bootstrapping 2PL-Models?
...chosen in the GoF.rasch()-function. Not being a
statistician, I was wondering whether the following simplification
(omit the "chi-squared-expressed model fit-step") would be appropriate:
GoF.ltm <- function(object, B = 50, ...){
liFits <- list()
for(i in 1:B){
rndDat <- rmvlogis(nrow(object$X), coef(object))
liFits[[i]] <- ltm(rndDat ~ z1)
}
distr <- sort(sapply(liFits, function(x)return(x$log.Lik)))
return(max(which(distr <= object$log.Lik))/length(distr))
}
The rationale behind was to directly use the sorted sequence of
(log)likelihoods of models fitt...