Marks

Marks are the visual encoding for data items. There are mainly 4 types of marks:

• points

• bars

• lines

• areas

Points

Points are mainly used in scatter plots.

Each point represents a data item, and its location typically represents two values.

Points are also used on maps.

Bars

Bars are used in bar charts.

Each bar represents a category and its height represents a value.

Bars can also be horizontal.

Lines

Lines are used in line charts.

They are usually used to show the change in a data item with time.

Lines are also used as links while modeling trees and networks.

Areas

Areas are used in symbol maps. They can also be used in tree maps to visualize hierarchical information.