Create new kfold.print method

NAMESPACE

@@ -56,6 +56,7 @@ S3method(print,compare.loo)
 S3method(print,compare.loo_ss)
 S3method(print,importance_sampling)
 S3method(print,importance_sampling_loo)
+S3method(print,kfold)
 S3method(print,loo)
 S3method(print,pareto_k_table)
 S3method(print,pseudobma_bb_weights)

R/print.R

@@ -105,6 +105,28 @@ print.importance_sampling <- function(x, digits = 1, plot_k = FALSE, ...) {
   invisible(x)
 }
 
+#' @export
+#' @rdname print.loo
+print.kfold <- function(x, digits = 1, plot_k = FALSE, ...) {
+  print.loo(x, digits = digits, ...)
+
+  if ("diagnostics" %in% names(x)) {
+    cat("------\n")
+    S <- dim(x)[1]
+    k_threshold <- ps_khat_threshold(S)
+    if (length(pareto_k_ids(x, threshold = k_threshold))) {
+      cat("\n")
+    }
+    print(pareto_k_table(x), digits = digits)
+    cat(.k_help())
+
+    if (plot_k) {
+      graphics::plot(x, ...)
+    }
+  }
+  return(invisible(x))
+  }
+
 # internal ----------------------------------------------------------------
 
 #' Print dimensions of log-likelihood or log-weights matrix

tests/testthat/_snaps/print_plot.md

@@ -2,3 +2,54 @@
 
     WAoAAAACAAQFAAACAwAAAAAOAAAAAT+2J8YDcP5s
 
+# print.loo supports kfold with pareto-k diagnostics - calibrated
+
+    Code
+      print(kfold1)
+    Output
+
+      Based on 10-fold cross-validation.
+
+                 Estimate   SE
+      elpd_kfold   -285.0  9.2
+      p_kfold         2.5  0.6
+      kfoldic       570.0 18.4
+      ------
+
+      All Pareto k estimates are good (k < 0.7).
+      See help('pareto-k-diagnostic') for details.
+
+# print.loo supports kfold with pareto-k diagnostics - miscalibrated
+
+    Code
+      print(kfold1)
+    Output
+
+      Based on 10-fold cross-validation.
+
+                 Estimate     SE
+      elpd_kfold  -5556.6  701.0
+      p_kfold       358.2  108.5
+      kfoldic     11113.1 1401.9
+      ------
+
+      Pareto k diagnostic values:
+                               Count Pct.    Min. ESS
+      (-Inf, 0.7]   (good)     245   93.5%   24      
+         (0.7, 1]   (bad)        8    3.1%   <NA>    
+         (1, Inf)   (very bad)   9    3.4%   <NA>    
+      See help('pareto-k-diagnostic') for details.
+
+# print.loo supports kfold without pareto-k diagnostics
+
+    Code
+      print(kfold1)
+    Output
+
+      Based on 10-fold cross-validation.
+
+                 Estimate     SE
+      elpd_kfold  -5556.6  701.0
+      p_kfold       358.2  108.5
+      kfoldic     11113.1 1401.9
+

tests/testthat/data-for-tests/kfold-notes.md

@@ -0,0 +1,31 @@
+## Test data for testing print method of `kfold` object
+
+### Case 1: All pareto-k values are good
+
+```{r}
+set.seed(123)
+dat <- dplyr::tibble(
+  x = rnorm(200),
+  y = 2 + 1.5 * x + rnorm(200, sd = 1)
+)
+
+fit <- brm(y ~ x, data = dat, seed = 42)
+kfold1 <- kfold(fit)
+saveRDS(kfold, "kfold-calibrated.Rds")
+```
+
+### Case 2: Some pareto-k values are problematic
+
+```{r}
+data(roaches, package = "rstanarm")
+roaches$sqrt_roach1 <- sqrt(roaches$roach1)
+
+fit_p <- brm(y ~ sqrt_roach1 + treatment + senior + offset(log(exposure2)),
+                data = roaches,
+                family = poisson,
+                prior = prior(normal(0,1), class = b),
+                refresh = 0)
+
+kfold2 <- kfold(fit_p)
+saveRDS(kfold2, "kfold-miscalibrated.Rds")
+```

tests/testthat/test_print_plot.R

@@ -185,3 +185,24 @@ test_that("mcse_loo returns NA when it should", {
 test_that("mcse_loo errors if not psis_loo object", {
   expect_error(mcse_loo(psis1), "psis_loo")
 })
+
+# print.loo kfold objects --------------------------------------------------
+
+test_that("print.loo supports kfold with pareto-k diagnostics - calibrated", {
+  kfold1 <- readRDS("data-for-tests/kfold-calibrated.Rds")
+
+  expect_snapshot(print(kfold1))
+})
+
+test_that("print.loo supports kfold with pareto-k diagnostics - miscalibrated", {
+  kfold1 <- readRDS("data-for-tests/kfold-miscalibrated.Rds")
+
+  expect_snapshot(print(kfold1))
+})
+
+test_that("print.loo supports kfold without pareto-k diagnostics", {
+  kfold1 <- readRDS("data-for-tests/kfold-miscalibrated.Rds")
+  kfold1$diagnostics <- NULL
+
+  expect_snapshot(print(kfold1))
+})