Instead of a histogram, we are going to make a smooth density plot. In this case we will not make an object, but instead render the plot with one line of code. Change the geometry in the code previously used to make a smooth density instead of a histogram.

1. Now we are going to make a density plot for males and females separately. We can do this using the group argument in aes. We assign groups via the global aesthetic mapping as each point needs to a group before making the calculations needed to estimate a density. Store the resulting ggplot object in p_group

2. We can also assign groups through the color argument. This distinguishes the groups by changing the color of the density outline. Change the code above to use color. Store the resulting ggplot object in p_color.

3. We can also assign groups through the fill argument. This distinguishes the groups by filling the geometry with different colors, like this:

heights %>% 
  ggplot(aes(height, fill = sex)) + 
  geom_density() 

However, here the second density is drawn over the other. We can make the curves more visible by using alpha blending to add transparency. Set the alpha parameter to 0.2 in the geom_density function to make this change. Store the resulting ggplot object in p_fill.