area() — Area chart

A line chart with the space underneath filled in.

plot + filled area

Key idea

• An area chart is a line chart with the space under the line filled in with colour.
• The shading draws your eye to the size, or volume, of the total.
• It works well for showing how a quantity builds up over time. (e.g. visitors: 200, 350, 500)
• Stacking areas (layering them) lets you see parts adding up to a whole over time. (e.g. Web 60 + Mobile 40 = 100)
• Use it when the overall amount matters more than the exact line value.

In plain words

A line showing a trend over time, with the space beneath it coloured in so the total size feels bigger.

Where you'd use it

• Track daily website visitors over a month. An area chart draws the visitor line and shades beneath it, so a rising filled wedge makes the growth from 200 to 800 visitors a day feel substantial at a glance.
• Plot monthly rainfall across a year; the filled area swells in the wet season and shrinks in the dry, giving an easy feel for total water volume over time.
• Show a company’s revenue climbing from $10k to $25k over five years, with the shaded area underneath emphasising how much the business has grown.

Frequently asked questions

Area chart or line chart?

Area emphasises cumulative total/volume — use it when filling down to zero is meaningful.