Accept posterior::draws objects in PPC/PPD functions (#542)

validate_predictions() now coerces posterior::draws objects (draws_matrix,
draws_array, draws_df, draws_rvars) to a plain matrix before validation,
matching the pattern already used by prepare_mcmc_array() on the MCMC side.

This lets users pass draws objects directly to ppc_* and ppd_* functions
without manually calling as.matrix() first.

Author: ishaan-arora-1

R/helpers-ppc.R

@@ -58,15 +58,20 @@ validate_y <- function(y) {
 #' Validate predictions (`yrep` or `ypred`)
 #'
 #' Checks that `predictions` is a numeric matrix, doesn't have any NAs, and has
-#' the correct number of columns.
+#' the correct number of columns. If `predictions` is a `posterior::draws`
+#' object it is first coerced to a matrix.
 #'
-#' @param predictions The user's `yrep` or `ypred` object (SxN matrix).
+#' @param predictions The user's `yrep` or `ypred` object (SxN matrix or a
+#'   `posterior::draws` object).
 #' @param `n_obs` The number of observations (columns) that `predictions` should
 #'   have, if applicable.
 #' @return Either throws an error or returns a numeric matrix.
 #' @noRd
 validate_predictions <- function(predictions, n_obs = NULL) {
-  # sanity checks
+  if (posterior::is_draws(predictions)) {
+    predictions <- posterior::as_draws_matrix(predictions)
+    predictions <- unclass(predictions)
+  }
   stopifnot(is.matrix(predictions), is.numeric(predictions))
   if (!is.null(n_obs)) {
     stopifnot(length(n_obs) == 1, n_obs == as.integer(n_obs))

tests/testthat/test-helpers-ppc.R

@@ -1,3 +1,4 @@
+library(posterior)
 source(test_path("data-for-ppc-tests.R"))
 source(test_path("data-for-mcmc-tests.R"))
 
@@ -113,6 +114,54 @@ test_that("get_interpolation_values catches impossible values", {
   )
 })
 
+# validate_predictions with posterior::draws objects ----------------------
+test_that("validate_predictions accepts draws_matrix", {
+  dm <- posterior::as_draws_matrix(yrep)
+  result <- validate_predictions(dm, ncol(yrep))
+  expect_true(is.matrix(result))
+  expect_equal(dim(result), dim(yrep))
+  expect_true(is.numeric(result))
+})
+
+test_that("validate_predictions accepts draws_array", {
+  da <- posterior::as_draws_array(yrep)
+  result <- validate_predictions(da)
+  expect_true(is.matrix(result))
+  expect_true(is.numeric(result))
+})
+
+test_that("validate_predictions accepts draws_df", {
+  ddf <- posterior::as_draws_df(yrep)
+  result <- validate_predictions(ddf)
+  expect_true(is.matrix(result))
+  expect_true(is.numeric(result))
+})
+
+test_that("validate_predictions accepts draws_rvars", {
+  dr <- posterior::as_draws_rvars(yrep)
+  result <- validate_predictions(dr)
+  expect_true(is.matrix(result))
+  expect_true(is.numeric(result))
+})
+
+test_that("ppc_dens_overlay works with draws_matrix input", {
+  dm <- posterior::as_draws_matrix(yrep)
+  p <- ppc_dens_overlay(y, dm)
+  expect_s3_class(p, "ggplot")
+})
+
+test_that("ppc_hist works with draws_matrix input", {
+  dm <- posterior::as_draws_matrix(yrep)
+  p <- ppc_hist(y, dm[1:8, ])
+  expect_s3_class(p, "ggplot")
+})
+
+test_that("ppc_stat works with draws_matrix input", {
+  dm <- posterior::as_draws_matrix(yrep)
+  p <- ppc_stat(y, dm)
+  expect_s3_class(p, "ggplot")
+})
+
 # ecdf_intervals ---------------------------------------------------------
 test_that("ecdf_intervals returns right dimensions and values", {
   lims <- ecdf_intervals(.0001, N = 100, K = 100, L = 1)