Briefle words · Data & charts
Dual axis
Also called secondary axis
A chart with two different value axes, one per series, whose independent ranges can make unrelated series appear to move together.
Say it to an AI
Line chart of monthly sessions and card spend, April to September, on one scale. Avoid a dual axis (secondary axis); instead plot indexed values (index = 100) rebased to April so the chart shows that sessions rose 40% while spend rose 8%, with a two-item colored key above the plot.
How an expert would brief the stronger version of “Sessions vs. spend chart”.
See it
Try it as a puzzle →Two-metric trend chart on the growth dashboard of a consumer fintech app.
Why: A's left axis runs 200k to 300k in blue and its right axis $4.00M to $4.50M in orange, and both lines end near the top.
Related words
Room 3 · Axes & scales
Learn “Dual axis” in a five-minute lesson