Helen
Your program makes no sense.
Try the following script
I <- 10
J <- 5
response <- matrix(0, 10, 5)
#function for probability of response
#revised but equivalent version of Helen's formula
pij <- function(a,b,theta) {1/(1+exp(-a*(theta-b)))}
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( j in 1:J ) {
response[i,j]<-ifelse(pij(a=a[j], b=b[j], theta[i]) < runif(1) , 0 ,1)
}
}
response
Helena <[email protected]>
Sent by: [email protected]
03/10/2010 11:03 PM
To
[email protected]
cc
Subject
[R] 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( j in 1:J ) {
ptemp <- runif(1)
pij <-
exp(a[j]*(theta[i]-b[j]))/(1+exp(a[j]*(theta[i]-b[j])))
response[i,j]<-ifelse(pij(b=b[j], a=a[j], theta[i]) <
ptemp , 0 ,1)
}
}
}
response
helena
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______________________________________________
[email protected] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
