Wrong fill values in a ggplot2 legend

Question

I have a geom_point plot over a ggmap with separate styling for shape and fill of the points and with colour kept constant. Here's the code:

ggmap(m) + 
geom_point(data = d, 
           aes(x = Longitude, y = Latitude, fill = Phylum, shape = Placecount), 
               colour = 'black', size = 2) +
scale_shape_manual(values = c(21,22))

The result is satisfactory except for the legend, where 'Phylum' is wrongly associated with black throughout.

Answer 1

You can manually adjust which the shape values are used in your fill legend (or any legend) with + guides(fill = guide_legend(override.aes = list(shape = 21))) . It looks like the default is shape = 1, which doesn't have support for fill, so you are just getting the solid black shapes.

Here is an example with mtcars:

ggplot(mtcars) +
    geom_point(aes(hp, mpg, fill = as.factor(cyl), shape = as.factor(am))) +
    scale_shape_manual(values = c(21,22)) +
    guides(fill = guide_legend(override.aes = list(shape = 21)))

plot with override_aes() :

plot without: