RuleMark

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Draws straight reference lines across the chart. Rules are useful for showing thresholds, averages, targets, or event markers. They can be horizontal (fixed y, spanning x) or vertical (fixed x, spanning y), and optionally bounded to create line segments.

Values can be static numbers or data field references. When a field name is provided, one rule is drawn per data row.

RuleMark is used inside a Chart container as one of the marks entries.

Constructor

nib.RuleMark(
    x=None,
    x_start=None,
    x_end=None,
    y=None,
    y_start=None,
    y_end=None,
    foreground_style=None,
    line_width=None,
    opacity=None,
)

Parameters

Parameter Type Default Description
x str \| float \| PlottableField \| PlottableValue None X-axis position for a vertical rule. Can be a static number, a field name, PlottableField, or PlottableValue.
x_start str \| float \| PlottableField \| PlottableValue None Starting x position for a bounded horizontal rule segment.
x_end str \| float \| PlottableField \| PlottableValue None Ending x position for a bounded horizontal rule segment.
y str \| float \| PlottableField \| PlottableValue None Y-axis position for a horizontal rule. Can be a static number, a field name, PlottableField, or PlottableValue.
y_start str \| float \| PlottableField \| PlottableValue None Starting y position for a bounded vertical rule segment.
y_end str \| float \| PlottableField \| PlottableValue None Ending y position for a bounded vertical rule segment.
foreground_style str \| PlottableField None Line color. Accepts hex strings, named colors, or a PlottableField.
line_width float None Width of the rule line in points.
opacity float None Opacity from 0.0 to 1.0.

Examples

Horizontal reference line (target)

import nib

chart = nib.Chart(
    data=[
        {"month": "Jan", "sales": 80},
        {"month": "Feb", "sales": 120},
        {"month": "Mar", "sales": 95},
    ],
    marks=[
        nib.BarMark(x="month", y="sales", foreground_style="#3B82F6"),
        nib.RuleMark(y=100, foreground_style="#EF4444", line_width=2),
    ],
    width=350,
    height=200,
)

Vertical reference line (event marker)

import nib

chart = nib.Chart(
    data=time_series_data,
    marks=[
        nib.LineMark(x="date", y="value"),
        nib.RuleMark(x="2024-06-15", foreground_style="#6366F1"),
    ],
    width=400,
    height=250,
)

Bounded horizontal segment

import nib

chart = nib.Chart(
    data=monthly_data,
    marks=[
        nib.LineMark(x="month", y="value"),
        nib.RuleMark(
            y=50,
            x_start="Jan",
            x_end="Jun",
            foreground_style="#10B981",
            line_width=1.5,
        ),
    ],
    width=400,
    height=200,
)

Labeled reference line with PlottableValue

import nib

chart = nib.Chart(
    data=sales_data,
    marks=[
        nib.BarMark(x="month", y="sales"),
        nib.RuleMark(
            y=nib.PlottableValue(100, label="Target"),
            foreground_style="#F59E0B",
            line_width=1.5,
        ),
    ],
    width=400,
    height=250,
)
PointMark RectMark