irt_ex <- data_frame(alpha = rep(seq(0, 1, length.out = 101), times = 3),
gamma = rep(c(.2, .35, .1), each=101),
beta = .5,
group = paste0("g", gamma, "b", beta),
pane = "Varying Discrimination") %>%
rbind(data_frame(alpha = rep(seq(0, 1, length.out = 101), times = 3),
gamma = .2,
beta = rep(c(.5, .25, .75), each=101),
group = paste0("g", gamma, "b", beta),
pane = "Varying Difficulty")) %>%
mutate(p = plogis((alpha - beta)/gamma),
group2 = rep(c(2, 1, 3, 5, 4, 6), each=101))
ggplot(irt_ex,
aes(alpha, p, group = group, color = group)) +
geom_line() + facet_wrap(~pane)
groups <- list(5, 4:5, 4:6)
for (i in 1:3) {
beta_plot <- ggplot(irt_ex %>% filter(group2 %in% groups[[i]]),
aes(alpha, p, group = factor(group2), color = factor(group2))) +
geom_line() + theme_bw() +
theme(legend.position="none") +
coord_cartesian(ylim = c(0, 1)) +
labs(x = "Positive Attitude", y = "Probability of a Positive Response") +
ggtitle("Varying Item Difficulty") +
scale_colour_manual(values = c("4" = "#FF6600","5" = "#000098","6" = "darkgreen"))
ggsave(paste0("paper/figures/ex_beta_plot", i, ".pdf"))
}
groups <- list(2, 1:2, 1:3)
for (i in 1:3) {
gamma_plot <- ggplot(irt_ex %>% filter(group2 %in% groups[[i]]),
aes(alpha, p, group = factor(group2), color = factor(group2))) +
geom_line() + theme_bw() +
theme(legend.position="none") +
coord_cartesian(ylim = c(0, 1)) +
labs(x = "Positive Attitude", y = "Probability of a Positive Response") +
ggtitle("Varying Item Discrimination") +
scale_colour_manual(values = c("1" = "#FF6600","2" = "#000098","3" = "darkgreen"))
ggsave(paste0("paper/figures/ex_gamma_plot", i, ".pdf"))
}
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