Distribution
Ridgeline / joy plot
Arranges distribution curves along an ordered or categorical axis.
- Plot
- Distribution
- Comparison
What it answers
How do distributions change across ordered groups?
- Shape
- Offset density ridges
- What it shows
- Shifting modes and changing spread.
Example
The question
How has the spread of delivery times shifted month by month?
Delivery time distribution by month (ridgeline)
Illustrative data. It belongs to no company.
When to use it
Use it when
Many ordered distribution groups with adequate samples.
Avoid it when
Heavy overlap, inconsistent scales or few observations.
How to read it
Read each ridge on the shared value axis and compare peak positions.
Note
Use consistent bandwidths and scales for comparisons.
The data you need
- Layout
- Long table
- Fields
- Group: text; Value: number
- One row is
- One raw observation belonging to a group. What is the grain?
- Rules
- Retain individual observations and group labels. State weighting and missing-data rules.
- Optional
- For box plots only, some tools accept Group,Q1,Median,Q3,WhiskerLow,WhiskerHigh plus separate outliers. Other distributions usually need raw data.
- Preparation
- Keep raw numeric observations, group them if needed and handle missingness explicitly. Choose bins, bandwidth or summary conventions as appropriate to this specific plot.
- Units
- The measurement axis retains its original unit. Frequency uses observations; normalised frequency divides by group sample size; density also depends on interval width.
Worked example
Example group summaries peak near 10,15,20. Show one density ridge per group; peaks move right. Use adequate raw data to estimate each ridge.
| Group | Value |
|---|---|
| A | 10 |
| A | 12 |
| A | 18 |
| B | 11 |
| B | 23 |