geom_mark_ellipse renders incorrect ellipse orientation with 3-point groups #354

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1. SotiriosVasileiadis commented on Feb 12, 2026

   

   SotiriosVasileiadis

   on Feb 12, 2026

   Last edited by SotiriosVasileiadis

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   not sure if it helps... cursor built a functional (at least for my so far run plots) version of the "mark_ellipse.R" script found in the https://github.com/thomasp85/ggforce/tree/main/R.

   Please test for proper functionality. My tests were not exhaustive and I am not fully familiar with ellipse functions.

   Could not upload the R extension file so I used a txt extension. You will find it here:
   mark_ellipse.txt

   If you want to test you can
   -> clone the https://github.com/thomasp85/ggforce repository in your computer
   -> replace the mark_ellipse.R with the linked mark_ellipse.txt
   -> change extension from txt to R
   -> install the local repo in R with

   devtools::install("my/local/ggforce_folder") 

   -> test with the following set kindly provided by https://github.com/julianzaugg at #214

   library(tidyverse)
   library(ggforce)
   
   test_dataset <- tibble(x     = c(-235, -220,  187, -100, -162,   8, 336, 159, 443, -77, -412), 
                          y     = c( -32, -147, -123,    6,  102, -14,  40,   6,  15, 115,   30),
                          group = c( "a",  "a",  "a",  "b",  "b", "b", "c", "c", "c", "d",  "d"))
   
   ggplot(test_dataset, aes(x = x, y = y, fill = group)) + 
     geom_mark_ellipse() +
     geom_point(shape = 21, size = 3, color = "black")

   Session info
   R: 4.5.2 (2025-10-31)
   Platform: OSX Tahoe 26.3
   ggforce: 0.5.0.9000 (github repository version https://github.com/thomasp85/ggforce)
   ggplot2: 4.0.2

   🎉React with 🎉2Reacted by gruensch and leoduo
2. leoduox commented on Feb 25, 2026

   

   leoduox

   on Feb 25, 2026

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   I also encountered the same problem.
   
3. gruensch commented on Feb 25, 2026

   

   gruensch

   on Feb 25, 2026

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   not sure if it helps... cursor built a functional (at least for my so far run plots) version of the "mark_ellipse.R" script found in the https://github.com/thomasp85/ggforce/tree/main/R.

   Please test for proper functionality. My tests were not exhaustive and I am not fully familiar with ellipse functions.

   Could not upload the R extension file so I used a txt extension. You will find it here: mark_ellipse.txt

   If you want to test you can -> clone the https://github.com/thomasp85/ggforce repository in your computer -> replace the mark_ellipse.R with the linked mark_ellipse.txt -> change extension from txt to R -> install the local repo in R with

   devtools::install("my/local/ggforce_folder")
   -> test with the following set kindly provided by https://github.com/julianzaugg at #214

   library(tidyverse)
   library(ggforce)

   test_dataset <- tibble(x = c(-235, -220, 187, -100, -162, 8, 336, 159, 443, -77, -412),
   y = c( -32, -147, -123, 6, 102, -14, 40, 6, 15, 115, 30),
   group = c( "a", "a", "a", "b", "b", "b", "c", "c", "c", "d", "d"))

   ggplot(test_dataset, aes(x = x, y = y, fill = group)) +
   geom_mark_ellipse() +
   geom_point(shape = 21, size = 3, color = "black")

   Session info
   R: 4.5.2 (2025-10-31)
   Platform: OSX Tahoe 26.3
   ggforce: 0.5.0.9000 (github repository version https://github.com/thomasp85/ggforce)
   ggplot2: 4.0.2

   So far, this fix works (just ran it over a couple of cases where geom_mark_ellipse failed to set the correct angle before).
   thank you!

   👍React with 👍1Reacted by Sotirios Vasileiadis (Σωτήριος Βασιλειάδης)
4. maartenciers commented on Jul 8, 2026

   

   maartenciers

   on Jul 8, 2026

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   Any update on this?