A multiline chart tracks several series across the same dimension, usually time. It can reveal changing patterns, but too many lines turn the display into visual spaghetti. section 6.1.1 section 6.4
The useful question is not merely whether every series fits on one chart, but whether users can compare the lines and understand the intended story. When crossings, labels, or gridlines create friction, simplify the view. section 6.4 section 6.1.1
Use these practical checks before committing to a multiline chart:
- Keep the number of lines manageable; if the series become difficult to follow, separate them into small multiples or give each line its own row while retaining the shared x-axis. section 6.4
- Remove automatically generated gridlines, axes, and labels that do not help the comparison, then add back only what users need. section 6.4
- Choose the chart for the question: a stacked bar chart can show weekly totals, but may make category comparisons harder. section 6.1.1
Avocado sales by category
A weekly sales view can plot bagged, bulk GTIN, and PLU 4046, 4225, and 4770 avocados as separate lines. That arrangement supports a time-trend question, but five lines can quickly become hard to trace. Small multiples or separate rows offer cleaner alternatives; stacked bars show total weekly sales more clearly, though category comparison becomes less direct. section 6.1.1
