Ggplot - Bars, rectangles with bases on x-axis (Geom_bar)

A bar geom makes the height of the bar proportional to:

• the number of cases in each group (default)
• or the sum of a column (using the weight aesthetic)

The geom_bar layer is used to produce 1d area plots:

• bar charts for categorical x,
• and histograms for continuous y.

geom_col() = geom_bar(stat="identity")

geom_bar plots by default the number of case. If you want a sum, you need to used the weight aesthetic.