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#' A Shiny app to experiment with the item response model
#'
#' @template args-dl
#' @template args-fit
#' @param item name of the item to visualize
#' @description
#'
#' When data \code{dl} and fitted model \code{fit} are provided, the
#' item parameters associated with \code{item} are loaded for
#' inspection.
#'
#' @template detail-response
#'
#' @importFrom rstan summary
#' @export
#' @examples
#' \donttest{
#' itemModelExplorer() # will launch a browser in RStudio
#' }
itemModelExplorer <- function(dl=NULL, fit=NULL, item=NULL) { # nocov start
want <- c("shiny","ggplot2")
if (requireNamespace(want, quietly = TRUE)) {
if (!is.null(dl)) {
assertDataFitCompat(dl, fit)
ii <- match(item, dl$nameInfo$item)
if (is.na(ii)) stop(paste("Cannot find item", item))
thrInd <- dl$TOFFSET[ii] + 1:dl$NTHRESH[ii] - 1L
if ("alpha" %in% names(fit@par_dims)) {
alphaName <- 'alpha'
if (length(fit@par_dims$alpha)) alphaName <- paste0("alpha[",ii,"]")
alpha <- summary(fit, pars=alphaName, .5)$summary[,'50%']
} else if (!is.null(dl[['alpha']])) {
alpha <- dl[['alpha']][ii]
} else {
stop("Where to find alpha?")
}
itemModelExplorer.default <-
list(scaleValue = dl$scale[ii],
discrimination = alpha,
thresholds = summary(fit, pars=paste0("threshold[",thrInd,"]"))$summary[,'mean'])
}
tryCatch(shiny::runApp(system.file('itemModelExplorer', package='pcFactorStan')),
finally=rm("itemModelExplorer.default", envir=globalenv()))
} else {
stop(paste0("Please install.packages(",deparse(want),") and try again"))
}
} # nocov end
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