Distribution

Frequency polygon

Connects bin frequencies at their midpoints to describe a distribution.

What it answers

How does frequency vary across numeric ranges?

The question

How do delivery times compare between our two warehouses?

Lines join the counts at each bin midpoint. Malmö peaks at 3 days; Lund peaks at 5 days and is more spread out.

Illustrative data. It belongs to no company.

Comparing binned distributions with less filled overlap.

When connections could be mistaken for observed values between bins.

Read frequencies at bin midpoints and follow the connecting line.

Can also use pre-binned midpoint and frequency columns.

Layout: Long table
Fields: Value: number
One row is: One raw numeric observation. What is the grain?
Rules: Use raw observations unless the chosen renderer explicitly accepts summaries or bins. Define missing-value treatment.
Optional: Optional frequency Weight. Pre-binned alternative: BinStart,BinEnd,Count; do not treat counts as raw values.
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.

A long table: one row per observation, few columns. New data adds rows.

Bins[10,15),[15,20),[20,25) have counts 3,1,1. Plot midpoints 12.5,17.5,22.5; the peak is the first bin.