Legend not clear with colour aesthetic and many levels of geom_point

[Sam Albers]

Hello there,

I am wondering it is possible to modify and ggplot2 legend such that the small grey boxes on the letter hand side on the plot that have points in them with the example below can be changed to fill the entire box with the corresponding legend colour while still maintaining points in the plot. I tried using the fill aesthetic hoping that might work but to no avail.

Basically I have a plot that has several factor levels and the little tiny point in the legend don't show up very nicely so I want to make the colour a bit clear.

Here is the example code:

ggplot(iris, aes(x=Sepal.Length,y=Petal.Length, colour=Species)) +
  geom_point(aes(fill=Species))

Thanks in advance!

Sam

[Dennis Murphy]

Hi:

The fill aesthetic in geom_point() only works for a few point shapes
(21-25), but it wouldn't change the result in the legend. This is not
exactly what you asked for, but one alternative is to increase the
point size in the legend, which you can do using guide_legend().
Extending your example,

library(ggplot2)
ggplot(iris, aes(x=Sepal.Length,y=Petal.Length, colour=Species)) +
geom_point() +
guides(colour = guide_legend(override.aes = list(size = 5)))

To manually fill the legend boxes post-hoc would be a non-trivial
task, although it may be possible with some combination of gtable and
grid graphics.

Dennis

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[Sam Albers]

Sorry for the late reply but building on Dennis's example, I could do something like this:

ggplot(iris, aes(x=Sepal.Length,y=Petal.Length, colour=Species)) +
  geom_point() +

  guides(colour = guide_legend(override.aes = list(size = 9, shape=15)))

Thanks for the help.

Sam