From 2f278f118c4256d9ebd81b415ab8f112cad5e052 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 15 Nov 2024 10:24:30 +0100
Subject: [PATCH 1/3] add `weight` aesthetic

---
 R/stat-ellipse.R | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/R/stat-ellipse.R b/R/stat-ellipse.R
index 5d1f41dd55..934e11c082 100644
--- a/R/stat-ellipse.R
+++ b/R/stat-ellipse.R
@@ -76,6 +76,8 @@ stat_ellipse <- function(mapping = NULL, data = NULL,
 #' @export
 StatEllipse <- ggproto("StatEllipse", Stat,
   required_aes = c("x", "y"),
+  optional_aes = "weight",
+  dropped_aes = "weight",
 
   setup_params = function(data, params) {
     params$type <- params$type %||% "t"
@@ -96,6 +98,9 @@ calculate_ellipse <- function(data, vars, type, level, segments){
   dfn <- 2
   dfd <- nrow(data) - 1
 
+  weight <- data$weight %||% rep(1, nrow(data))
+  weight <- weight / sum(weight)
+
   if (!type %in% c("t", "norm", "euclid")) {
     cli::cli_inform("Unrecognized ellipse type")
     ellipse <- matrix(NA_real_, ncol = 2)
@@ -104,11 +109,12 @@ calculate_ellipse <- function(data, vars, type, level, segments){
     ellipse <- matrix(NA_real_, ncol = 2)
   } else {
     if (type == "t") {
-      v <- MASS::cov.trob(data[,vars])
+      # Prone to convergence problems when `sum(weight) != nrow(data)`
+      v <- MASS::cov.trob(data[,vars], wt = weight * nrow(data))
     } else if (type == "norm") {
-      v <- stats::cov.wt(data[,vars])
+      v <- stats::cov.wt(data[,vars], wt = weight)
     } else if (type == "euclid") {
-      v <- stats::cov.wt(data[,vars])
+      v <- stats::cov.wt(data[,vars], wt = weight)
       v$cov <- diag(rep(min(diag(v$cov)), 2))
     }
     shape <- v$cov

From 43611385ab4ec938e24d8a3a28568583eba83957 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 15 Nov 2024 10:26:36 +0100
Subject: [PATCH 2/3] add news bullet

---
 NEWS.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/NEWS.md b/NEWS.md
index 0c493a8f58..33833f488d 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,6 @@
 # ggplot2 (development version)
 
+* Added `weight` aesthetic for `stat_ellipse()` (@teunbrand, #5272)
 * Custom and raster annotation now respond to scale transformations, and can
   use AsIs variables for relative placement (@teunbrand based on 
   @yutannihilation's prior work, #3120)

From fa0b587ec5650d8e5c9c1807b1d25e0baccfa3db Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 15 Nov 2024 10:28:50 +0100
Subject: [PATCH 3/3] document aesthetics

---
 R/stat-ellipse.R    |  1 +
 man/stat_ellipse.Rd | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/R/stat-ellipse.R b/R/stat-ellipse.R
index 934e11c082..d462bf3575 100644
--- a/R/stat-ellipse.R
+++ b/R/stat-ellipse.R
@@ -20,6 +20,7 @@
 #' @param segments The number of segments to be used in drawing the ellipse.
 #' @inheritParams layer
 #' @inheritParams geom_point
+#' @eval rd_aesthetics("stat", "ellipse")
 #' @export
 #' @examples
 #' ggplot(faithful, aes(waiting, eruptions)) +
diff --git a/man/stat_ellipse.Rd b/man/stat_ellipse.Rd
index 4bc30ef863..8ef16d92cc 100644
--- a/man/stat_ellipse.Rd
+++ b/man/stat_ellipse.Rd
@@ -125,6 +125,18 @@ the default plot specification, e.g. \code{\link[=borders]{borders()}}.}
 The method for calculating the ellipses has been modified from
 \code{car::dataEllipse} (Fox and Weisberg 2011, Friendly and Monette 2013)
 }
+\section{Aesthetics}{
+
+\code{stat_ellipse()} understands the following aesthetics (required aesthetics are in bold):
+\itemize{
+\item \strong{\code{\link[=aes_position]{x}}}
+\item \strong{\code{\link[=aes_position]{y}}}
+\item \code{\link[=aes_group_order]{group}}
+\item \code{weight}
+}
+Learn more about setting these aesthetics in \code{vignette("ggplot2-specs")}.
+}
+
 \examples{
 ggplot(faithful, aes(waiting, eruptions)) +
   geom_point() +