---
title: "Visual-context and testlet IRT"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Visual-context and testlet IRT}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(collapse = TRUE, comment = "#>", eval = FALSE)
library(eyeprocess)
```

Items displayed on the same screen, page, diagram, or stimulus can share presentation-context variance. `fit_visual_context_irt()` models that known design dependence as a separate testlet/context dimension rather than silently treating every item as independent.

```{r}
registry <- visual_context_registry(
  item_metadata,
  item = "item_id",
  context = "screen_id"
)

fit <- fit_visual_context_irt(
  response_matrix,
  registry = registry,
  context = "screen_3"
)

compare_visual_context_irt(fit)
context_factor_effects(fit)
audit_visual_context_dependence(fit)
plot(fit, type = "loadings")
plot(fit, type = "difficulty_change")
plot(fit, type = "context_registry")
```

The context dimension represents shared presentation context unless independent substantive theory and validation justify another interpretation.