Finding Relationships
Relationship charts are used to show a connection or correlation between two or more variables. They help answer questions like: "Does an increase in advertising spend lead to an increase in sales?"
Scatter Plots
The undisputed king of relationship visualization. By plotting data points on horizontal and vertical axes, a scatter plot reveals patterns, clusters, and outliers instantly.
Bubble Charts
A scatter plot that adds a third variable, encoded by the size of the circle (area, not radius).
| Rule | Why |
|---|---|
| Size circles by Area, not Radius | If value A is twice as large as value B, and you double the radius, the resulting circle is four times larger in area, grossly exaggerating the difference. Formula: r = sqrt(value / PI) |
| Use Opacity | Bubbles overlap. Using semi-transparent fills allows smaller bubbles hidden behind larger ones to remain visible. |
Common Mistakes
- Overplotting: When thousands of points are drawn on top of each other, the plot becomes a solid blob. Solutions: Decrease point size, increase transparency, or use a 2D density plot (hexbin).
- Assuming Causation: A scatter plot shows correlation. It does not prove that X causes Y.
Next Steps
Check out our Axis Calculator to set up the scales for your scatter plot.