#steps towards a Rasch modeling program for IRT #first, estimate the item difficulties "irt.item.diff.rasch" <- function(items) { ncases <- nrow(items) item.mean <- colMeans(items,na.rm=TRUE) item.mean[item.mean<(1/ncases)] <- 1/ncases irt.item.diff.rasch <- log((1/item.mean)- 1) }