How do I get a more logical scale bar?

Question

I've plotted point data of parakeet observations (fake for now) across the UK with the observations coloured by the population density of the area the observation was made in. I have a continuous scale bar as I want but the scale itself is awkwardly annotated. How can I plot it with more even dividers?

Here is the code:

############################ #PLOT OBSERVATIONS x POP_DENS ############################

ggplot() +
  geom_polygon(data = UK, aes(x=long, y = lat, group = group), fill="gray14", alpha=0.7) +
  geom_point(data=paratweets_4, aes(x=coords.x1, y=coords.x2, color=pop_dens, shape=Occupancy), size=2,stroke=FALSE) +
  scale_color_viridis(option="magma", trans="log", name="Human Population Density (km2)") +
  theme_minimal() + ylim(50,59) + coord_map() + 
  ggtitle("Parakeet Observations")

Here is the map:

score 0 · Accepted Answer · answered Feb 17 '21 at 10:47

One strategy would be to make a column for the scale bar, with a metric that makes sense to you. For example,

df %>% 
  mutate(scale_column = case_when(
    pop_dens == 0 ~ "0",
    pop_dens > 0 & pop_dens < 100 ~ "0-100",
    pop_dens > 100 & pop_dens < 1000 ~ "100-999",
    pop_dens > 1000 & pop_dens < 2000 ~ "1000-1999",
  ))

Then using that column as your scale. Another option would be to modify the breaks of the scales. However, I would argue that in this case it might make sense to not have scale by color, but rather change the size of the points.

How do I get a more logical scale bar?

1 Answers1