set.seed(1)
x1 <- sample(1:5, 100, replace = TRUE)
x2 <- sample(1:5, 100, replace = TRUE)
x3 <- sample(1:5, 100, replace = TRUE)
X <- cbind.data.frame(x1, x2, x3)
mod <- pirtmodel(X)
out <- model_goodness_poly(mod)
out
autoplot(out)
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