summary.ltm <-
function (object, robust.se = FALSE, ...) {
if (!inherits(object, "ltm"))
stop("Use only with 'ltm' objects.\n")
if (object$IRT.param)
irt <- IRT.parm(object, TRUE, robust = robust.se)
coefs <- if (object$IRT.param) irt$parms else object$coef
Var.betas <- vcov(object, robust = robust.se)
se <- if (!is.null(constraint <- object$constraint)) {
p <- nrow(coefs)
res <- matrix(NA, p, ncol(coefs))
res[-((constraint[, 2] - 1) * p + constraint[, 1])] <- if (object$IRT.param) irt$se else sqrt(diag(Var.betas))
c(res)
} else {
if (object$IRT.param) irt$se else sqrt(diag(Var.betas))
}
z.vals <- c(coefs)/se
coef.tab <- cbind(value = c(coefs), std.err = se, z.vals = z.vals)
p <- nrow(coefs)
rownames(coef.tab) <- if (object$IRT & (object$ltst$factors == 1 & !object$ltst$quad.z1))
paste(rep(colnames(coefs), each = p), rownames(coefs), sep = ".")
else
paste(rep(object$ltst$nams, each = p), rownames(coefs), sep = ".")
out <- list(coefficients = coef.tab, Var.betas = Var.betas)
out$logLik <- object$log.Lik
out$AIC <- -2 * object$log.Lik + 2 * length(coefs)
out$BIC <- -2 * object$log.Lik + log(nrow(object$X)) * length(coefs)
out$max.sc <- object$max.sc
out$conv <- object$conv
out$counts <- object$counts
out$call <- object$call
out$ltst <- object$ltst
out$control <- object$control
out$attr <- attr(object$X, "items")
out$ancr <- attr(object$X, "anchoring")
class(out) <- "summ.ltm"
out
}
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