add new test file

Author: philchalmers

tests/tests/test-18-LLTM.R

@@ -0,0 +1,39 @@
+context('LLTM')
+
+test_that('LLTM', {
+    set.seed(42)
+    a <- matrix(rep(1,30))
+    d <- rep(c(1,0, -1),each = 10)  # first easy, then medium, last difficult
+    dat <- simdata(a, d, 1000, itemtype = '2PL')
+    itemdesign <- data.frame(difficulty =
+        factor(c(rep('easy', 10), rep('medium', 10), rep('hard', 10))))
+    rownames(itemdesign) <- colnames(dat)
+
+    lltm <- mirt(dat, itemtype = 'Rasch', SE=TRUE, verbose=FALSE,
+        item.formula = ~ 0 + difficulty, itemdesign=itemdesign)
+    expect_equal(as.numeric(coef(lltm, simplify=TRUE)$items[1:2,1]), c(0.9587247, 0.9587247), tol=1e-2)
+    expect_equal(as.numeric(coef(lltm, printSE=TRUE)[[1]][2, 1:3]), c(0.03886556, 0.03898911, 0.03769205), tol=1e-2)
+    expect_equal(extract.mirt(lltm, 'condnum'), 6.633144, tol=1e-2)
+
+    # additional information for LLTM
+    oo <- plot(lltm)
+    expect_is(oo, 'trellis')
+    ifit <- itemfit(lltm)
+    expect_equal(ifit$S_X2[1:3], c(20.06072, 20.90161, 23.48163), tol=1e-2)
+    eap <- fscores(lltm)
+    expect_equal(eap[1:3], c(1.0141828, -0.2427042, -0.2427042))
+
+    # using unconditional modeling for first four items
+    itemdesign.sub <- itemdesign[5:nrow(itemdesign), , drop=FALSE]
+    lltm.4 <- mirt(dat, itemtype = 'Rasch', SE=TRUE, verbose=FALSE,
+        item.formula = ~ 0 + difficulty, itemdesign=itemdesign.sub)
+    cfs <- coef(lltm.4, simplify=TRUE)$items
+    expect_equal(as.vector(cfs[c(1,5), 1:3]), c(0, .9063842, numeric(4)), tol=1e-2)
+    expect_equal(anova(lltm, lltm.4)$p[2], 0.04288353, tol=1e-2)
+
+})
+
+test_that('MLTM', {
+
+})
+