Make stat_ellipse {ggplot2} outline geom_point fill color

Question

I have a scatterplot with 15 groupings. I am using geom_point() with shape = 21 so that I can have fill and color (outline color). I am using black for the outline color to give better contrast between the similar colors in my legend. When I add a stat_ellipse() though, it makes the ellipse outline black.

I want this, with black outlines around the points:

groupings <- paste0("Group", 1:15)
iris$group <- rep(groupings, 10)

iris_plot <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width)) + geom_point(aes(Sepal.Length, Sepal.Width, colour = factor(iris$group))) + stat_ellipse(data = iris, aes(color = factor(iris$group)))

iris_plot

But when I add the black outlines around the points, it turns my ellipses black, making them impossible to interpret.

library(RColorBrewer)

groupings <- paste0("Group", 1:15)
iris$group <- rep(groupings, 10)

fill_colors <- scales::hue_pal()(15)
outline_colors <- rep("black", 15)

iris_plot <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width)) + geom_point(aes(Sepal.Length, Sepal.Width, colour = factor(iris$group), fill = factor(iris$group)), shape = 21) + stat_ellipse(data = iris, aes(color = factor(iris$group))) + scale_colour_manual(name = "Grouping", labels = sort(unique(factor(iris$group))), values = outline_colors) + scale_fill_manual(name = "Grouping", labels = sort(unique(factor(iris$group))), values = fill_colors)

iris_plot

I do not want a fill color because there is so much overlap between ellipses that it becomes impossible to see anything.

Thank you for your time.

Answer 1

I think you need to pass color outside aes for geom_point, otherwise when you are applying scale_color_manual, it will apply both for geom_point and stat_ellipse:

iris_plot <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width)) + 
  geom_point(aes(Sepal.Length, Sepal.Width,fill = group), color = "black", shape = 21) + 
  stat_ellipse(data = iris, aes(color = group)) + 
  scale_fill_manual(name = "Grouping", labels = sort(unique(factor(iris$group))), values = fill_colors)+
  scale_color_manual(name = "Grouping", values = fill_colors,  labels = sort(unique(factor(iris$group))))

iris_plot