geom_tri_tern fails to include some cases

[Markus Englund]

I cannot get geom_tri_tern to count all my cases. It seems that some extreme values are not included in the counts.

EDIT: after some more checking it seems that points on bins' boundaries are excluded from the count.

I’m using version 3.4.1

If I run the code snippet below, only one of three points are included in the counts shown by the geom_tri_tern layer.

df = data.frame(x = c(0, 80, 50),
                y = c(0, 20, 50),
                z = c(100, 0, 0))
ggtern(df, aes(x, y, z)) +
  geom_tri_tern(bins = 5, aes(fill = after_stat(count))) +
  geom_point(size = 5)

‌

[Nicholas Hamilton]

Without running the code myself (its 3am here, I’ll investigate tomorrow), from recollection, I think it is because the point is sitting on the junction of several regions, and therefore contributes only 1/3 (or perhaps 1/6th if in the middle) of a point count for each surrounding triangle.

Try duplicating the point, by 3x (or 6), ie, in your frame, ie, replicate the offending point multiple times, to test my above hypothesis.