Adjusting point color

ggplot(___) + 
  geom_point(
    mapping = aes(x = ___, y = ___, 
                  color = ___, 
                  size  = ___),
    alpha  = ___
  )
View Interactive Version

Typically, the point color is used to introduce a new dimension to a scatter plot. In ggplot we use the color aesthetic to specify the mapping of a variable to the color of the points.

For the gapminder_2007 dataset we can plot the GDP per capita gdpPercap vs. the life expectancy lifeExp as follows:

Input
ggplot(gapminder_2007) + 
  geom_point(aes(x = gdpPercap, y = lifeExp))

To color each point based on the continent of each country we can use:

Input
ggplot(gapminder_2007) + 
  geom_point(aes(x = gdpPercap, y = lifeExp,
                 color = continent))

We see that in the resulting plot each point is colored differently based on the continent of each country. ggplot uses the coloring scheme based on the categorical data type of the variable continent.

By contrast, let’s see how the plot looks like if we color the points by the numeric variable population pop:

Input
ggplot(gapminder_2007) + 
  geom_point(aes(x = gdpPercap, y = lifeExp,
                 color = pop))

The scale immediately changes to continuous as it can be seen in the legend and the light-blue points are now the countries with the highest population number (China and India).

Specify additional aesthetics for points