> ## Documentation Index
> Fetch the complete documentation index at: https://cubed3-feat-druid-driver-streaming.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Line

> Track how a measure changes over time or across an ordered dimension.

Line charts connect data points with a continuous line. Use them when the direction and rate of change matter — trends over time, trajectories of multiple series, or any ordered dimension where continuity is meaningful.

## Variants

### Single series

One measure plotted against a time or ordered dimension. The simplest and most common use case.

### Multi-series

Multiple lines plotted on the same axes. Map a second dimension to the **Color** channel to split one measure into one line per dimension value, or add multiple measures to the Y axis to plot them as separate series.

### With reference line

A horizontal reference line marks a target, threshold, or benchmark. Added via the **Axes** section of the Style tab.

## Reference lines

Add a horizontal reference line in the **Y axis** section of the Style tab. Set the value, label, color, and line style (solid, dashed, or dotted). Multiple reference lines are supported.

See [Axes](/docs/explore-analyze/charts/configuration/axes) for the full configuration reference.

## Axis behavior

Line charts use a temporal X axis for time dimensions — continuous, time-aware, and not constrained to the result set. For non-time dimensions, the axis is ordinal and follows the result set sort order. Gaps in the line indicate missing data points.

## Combining with bars

To layer a line on top of a bar chart, add a second series to the Y axis, set its mark type to **Line** in [series configuration](/docs/explore-analyze/charts/configuration/series-configuration), and assign it to the right Y axis for a dual-axis layout.