Reference Line

Cookbook

Reference Line

Use this when: You need to add a horizontal reference line at value on the y-axis. Outside the mark’s (padded) y-domain, draws nothing rather than clipping to an edge.

Reference Line

Usage

from dataviz import Plot, save


def main() raises:
    var months: List[String] = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]
    var revenue: List[Float64] = [42.0, 48.0, 45.0, 61.0, 55.0, 58.0]

    var plot = (
        Plot()
        .mark_bar()
        .encode_categorical(x=months, y=revenue)
        .labels(title="Monthly Revenue", subtitle="Actual vs. target, $M")
        .annotate_line(60.0, label="target")
        .annotate_line(51.5, label="average")
    )
    save(plot, "docs/src/examples/out_annotate_line.svg")

Related recipes: Vertical Reference Line

Relevant API: Plot annotations

Reference Band Ridgeline Overlap