BarMark

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Displays data as rectangular bars, ideal for comparing discrete categories or showing distributions. Bars can be oriented vertically or horizontally and support stacking for multi-series comparisons.

The orientation is determined by which fields are categorical versus quantitative. For vertical bars, x is typically categorical and y is quantitative. Swap the fields for horizontal bars.

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

Constructor

nib.BarMark(
    x=None,
    y=None,
    width=None,
    height=None,
    foreground_style=None,
    stacking=None,
    corner_radius=None,
    opacity=None,
)

Parameters

Parameter Type Default Description
x str \| PlottableField None Data field for the x-axis. For vertical bars, this is typically the categorical field.
y str \| PlottableField None Data field for the y-axis. For vertical bars, this is the quantitative field (bar height).
width float None Fixed bar width in points. If not specified, bars are sized automatically.
height float None Fixed bar height in points. If not specified, bars are sized by y data values.
foreground_style str \| PlottableField None Bar fill color. Accepts hex strings, named colors, or a PlottableField to color bars by category (creates grouped or stacked bars).
stacking StackingMethod \| str None How to stack bars when multiple series overlap. Options: STANDARD (stacked), NORMALIZED (100% stacked), CENTER (centered). Default is no stacking (bars are grouped side by side).
corner_radius float None Radius for rounded bar corners in points.
opacity float None Opacity from 0.0 to 1.0.

Examples

Simple vertical bar chart

import nib

def main(app: nib.App):
    chart = nib.Chart(
        data=[
            {"product": "A", "sales": 120},
            {"product": "B", "sales": 200},
            {"product": "C", "sales": 150},
        ],
        marks=[nib.BarMark(x="product", y="sales", foreground_style="#10B981")],
        width=300,
        height=200,
    )
    app.build(chart)

nib.run(main)

Horizontal bar chart

import nib

chart = nib.Chart(
    data=[
        {"lang": "Python", "users": 45},
        {"lang": "JavaScript", "users": 38},
        {"lang": "Rust", "users": 12},
    ],
    marks=[nib.BarMark(x="users", y="lang")],
    width=350,
    height=200,
)

Stacked bar chart

import nib

data = [
    {"quarter": "Q1", "revenue": 100, "region": "US"},
    {"quarter": "Q1", "revenue": 80, "region": "EU"},
    {"quarter": "Q2", "revenue": 120, "region": "US"},
    {"quarter": "Q2", "revenue": 90, "region": "EU"},
]

chart = nib.Chart(
    data=data,
    marks=[
        nib.BarMark(
            x="quarter",
            y="revenue",
            foreground_style=nib.PlottableField("region"),
            stacking=nib.StackingMethod.STANDARD,
        ),
    ],
    legend=nib.ChartLegend(position="bottom"),
    width=400,
    height=250,
)

Styled bars with rounded corners

import nib

chart = nib.Chart(
    data=product_data,
    marks=[
        nib.BarMark(
            x="product",
            y="revenue",
            foreground_style="#8B5CF6",
            corner_radius=4,
        ),
    ],
    width=300,
    height=200,
)
LineMark AreaMark