From 55518e0830f27969262964a4a43c2fafab3f767d Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Wed, 25 Feb 2026 01:02:37 +0000
Subject: [PATCH] Optimize marg_pabs in R/utils.R

Replaced inefficient loop-based dataframe construction and `bind_rows` in `marg_pabs` with vectorized subsetting. This significantly improves performance and removes the dependency on `dplyr` for this function.

The logic for `est_samples` (posterior draws) remains consistent with the original implementation: `est_samples` is flattened column-wise (draws for observation 1, then observation 2, etc.), which corresponds to the vectorized expansion of `newdata` (row 1 repeated n_sim times, then row 2 repeated n_sim times).

This change improves performance by avoiding repeated memory allocations and dataframe binding operations. It also makes the function more robust by relying on base R instead of the suggested `dplyr` package.

Co-authored-by: lcgodoy <24809942+lcgodoy@users.noreply.github.com>
---
 R/utils.R | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/R/utils.R b/R/utils.R
index 3bd6dfc..9207237 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -222,18 +222,15 @@ marg_pabs <- function(drm, newdata) {
     drm$stanfit$draws(variables = c("beta_t"),
                       format = "draws_matrix")
   n_sim <- NROW(est_samples)
-  output <- vector(mode = "list", length = NROW(newdata))
   est_samples <-
     tcrossprod(est_samples, new_x)
   est_samples <- stats::plogis(c(est_samples))
-  rownames(newdata) <- NULL
-  for (i in seq_along(output)) {
-    output[[i]] <-
-      cbind.data.frame(newdata[i, , drop = FALSE], iter = seq_len(n_sim)) |>
-      suppressWarnings()
-  }
-  output <- dplyr::bind_rows(output)
-  output <- dplyr::mutate(output, prob_abs = est_samples)
+  n_obs <- nrow(newdata)
+  idx <- rep(seq_len(n_obs), each = n_sim)
+  output <- newdata[idx, , drop = FALSE]
+  output$iter <- rep(seq_len(n_sim), times = n_obs)
+  output$prob_abs <- est_samples
+  rownames(output) <- NULL
   return(output)
 }