pie() — Pie chart

A round chart where each slice shows one group’s share of the whole.

pie(x, labels)

Key idea

• A pie chart splits a circle into slices that are parts of one whole. (e.g. 40% + 35% + 25% = 100%)
• Each slice's angle reflects its share of the total. (e.g. half the pie = 50%)
• It works best with only a few categories. (e.g. 3 to 5 slices)
• All slices together must add up to 100%.
• Hard to compare slices that are close in size by eye. (e.g. 33% vs 31%)

Definition

$${\theta }_i=\frac{x_i}{{\sum }_j{x}_j}\times 360^{\circ }$$

$x_i$

a single group value

${\sum }_j{x}_j$

the total of all groups

${\theta }_i$

the slice angle in degrees

In plain words

Cut a whole pie into slices, one slice per group. Just look to see who got the biggest piece — the widest slice wins.

Where you'd use it

• A monthly budget splits into rent $1000, food $400, and fun $100. A pie shows rent filling about two-thirds of the circle, making it obvious where most of the money goes.
• An election gave three candidates 50%, 30%, and 20% of the vote. The pie cuts into a half-circle slice and two smaller wedges, showing at a glance who won and by how much.
• For a day split into sleep 8 h, work 8 h, and play 8 h, the pie shows three equal slices of one-third each, instantly conveying a balanced day.

Worked example 1

How many games sold in each type for Manic Mango: Sports 27,500, Strategy 11,500, Action 6,000, Shooter 3,500, Other 1,500. With one look, Sports grabs the biggest slice.

Frequently asked questions

Pie or bar chart?

Bars are easier to compare. Use a pie only for a few parts of one whole.