Section $1$ exercises:

$1.(5$ pts$.)$ Run ggplot$($data $=$ gapminder$07).$ What do you see and why?

$2.(5$ pts$.)$ How many rows are in gapminder$07?$ How many columns?

Aesthetic mappings

The plot above shows that people in rich countries, on average, live longer than people in poor countries. However,

it tells us very little about which countries belong to different categories. For example, where are the different

continents on this graph? We saw in the data frame that it contains information about continents. How do we

bring this information into the graph?

In ggplot$2,$ you do this by adding an additional variable, like continent, to the two dimensional scatterplot by

mapping it to an aesthetic. An aesthetic is a visual property of the objects in your plot. Aesthetics include things

like the size, the shape, or the color of your points. You can display a point $($like the one below$)$ in different ways

by changing the values of its aesthetic properties.

Figure $1$:

Since we already use the word $$value$$ to describe data, let$$s use the word $$level$$ to describe aesthetic properties.

You can convey information about your data by mapping the aesthetics in your plot to the variables in your dataset.

For example, you can map the colors of your points to the continent variable to reveal the continent of each

country.

ggplot$($data $=)+$

$($mapping $=$ aes$())$