Data Series

A data series is a set of related data points that belong together and are drawn as a single group on a chart — one line, one colour of bars, or one cloud of points.

A series is the unit a chart is built from. Each series represents one variable measured across the chart's categories or time periods, and it is given a consistent visual identity — a single colour or marker — so it can be followed as a whole. A chart with one series shows one story; a chart with several lets you compare those stories side by side.

How a data series works

Every point in a series shares the same meaning — they are all measurements of the same thing — and differ only in where they fall along the chart. On a line chart, a series is one connected line; on a bar chart, it is all the bars of one colour; on a scatter plot, it is all the points of one shape. When a chart holds more than one series, a legend names them so the colours are not ambiguous.

A concrete example

Consider a chart comparing two products' monthly sales across a year. "Product A" is one data series — twelve points, one per month, drawn as a green line. "Product B" is a second series, twelve more points, drawn in blue. Each line tells that product's story over the year, and placing them on the same axes lets you see at a glance which sold more and when one overtook the other.

Related terms

A data series is made of individual data points, is identified by a legend when several share a chart, and is positioned by the chart's axes. Comparing multiple series over time is the heart of the line chart guide.