```
ggplot(mpg, aes(cty, hwy)) +
geom_point()
ggplot(mpg, aes(cty, hwy)) +
geom_count()
# Best used in conjunction with scale_size_area which ensures that
# counts of zero would be given size 0. Doesn't make much different
# here because the smallest count is already close to 0.
ggplot(mpg, aes(cty, hwy)) +
geom_count() +
scale_size_area()
# Display proportions instead of counts -------------------------------------
# By default, all categorical variables in the plot form the groups.
# Specifying geom_count without a group identifier leads to a plot which is
# not useful:
d <- ggplot(diamonds, aes(x = cut, y = clarity))
d + geom_count(aes(size = ..prop..))
# To correct this problem and achieve a more desirable plot, we need
# to specify which group the proportion is to be calculated over.
d + geom_count(aes(size = ..prop.., group = 1)) +
scale_size_area(max_size = 10)
# Or group by x/y variables to have rows/columns sum to 1.
d + geom_count(aes(size = ..prop.., group = cut)) +
scale_size_area(max_size = 10)
d + geom_count(aes(size = ..prop.., group = clarity)) +
scale_size_area(max_size = 10)
```

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