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.. currentmodule:: altair
.. _user-guide-arc-marks:
Arc
~~~
Arc marks are circular arcs defined by a center point plus angular and radial extents.
Arc marks are typically used for radial plots such as pie and donut charts.
Arc Mark Properties
-------------------
.. altair-plot::
:hide-code:
:div_class: properties-example
import altair as alt
import numpy as np
import pandas as pd
rad_slider = alt.binding_range(min=0, max=100, step=1)
rad_var = alt.param(bind=rad_slider, value=0, name="radius")
rad2_slider = alt.binding_range(min=0, max=100, step=1)
rad_var2 = alt.param(bind=rad_slider, value=50, name="radius2")
theta_slider = alt.binding_range(min=-2 * np.pi, max=2 * np.pi)
theta_var = alt.param(bind=theta_slider, value=-0.73, name="theta_single_arc")
theta_slider2 = alt.binding_range(min=-2 * np.pi, max=2 * np.pi)
theta2_var = alt.param(bind=theta_slider, value=0.73, name="theta2_single_arc")
corner_slider = alt.binding_range(min=0, max=50, step=1)
corner_var = alt.param(bind=corner_slider, value=0, name="cornerRadius")
pad_slider = alt.binding_range(min=0, max=np.pi / 2)
pad_var = alt.param(bind=pad_slider, value=0, name="padAngle")
source = pd.DataFrame({"category": [1, 2, 3, 4, 5, 6], "value": [4, 6, 10, 3, 7, 8]})
c1 = alt.Chart(source, title="Single Arc").mark_arc(
radius=rad_var,
radius2=rad_var2,
theta=theta_var,
theta2=theta2_var,
cornerRadius=corner_var,
padAngle=pad_var,
)
c2 = (
alt.Chart(source, title="Stacked Arcs")
.mark_arc(
radius=rad_var,
radius2=rad_var2,
cornerRadius=corner_var,
padAngle=pad_var,
)
.encode(
theta=alt.Theta(field="value", type="quantitative"),
color=alt.Color(field="category", type="nominal"),
)
)
alt.hconcat(c1.properties(width=200), c2.properties(width=200)).add_params(
rad_var, rad_var2, theta_var, theta2_var, corner_var, pad_var
)
An ``arc`` mark definition can contain any :ref:`standard mark properties <mark-properties>`
and the following special properties:
.. altair-object-table:: altair.MarkDef
:properties: radius radius2 innerRadius outerRadius theta theta2 cornerRadius padAngle radiusOffset radius2Offset thetaOffset theta2Offset
Examples
--------
We can create a pie chart by encoding ``theta`` or ``color`` arc marks.
.. altair-plot::
import pandas as pd
import altair as alt
source = pd.DataFrame({"category": [1, 2, 3, 4, 5, 6], "value": [4, 6, 10, 3, 7, 8]})
alt.Chart(source).mark_arc().encode(
theta=alt.Theta(field="value", type="quantitative"),
color=alt.Color(field="category", type="nominal"),
)
Setting ``innerRadius`` to non-zero values will create a donut chart.
.. altair-plot::
import pandas as pd
import altair as alt
source = pd.DataFrame({"category": [1, 2, 3, 4, 5, 6], "value": [4, 6, 10, 3, 7, 8]})
alt.Chart(source).mark_arc(innerRadius=50).encode(
theta=alt.Theta(field="value", type="quantitative"),
color=alt.Color(field="category", type="nominal"),
)
You can also add a text layer to add labels to a pie chart.
.. altair-plot::
import pandas as pd
import altair as alt
source = pd.DataFrame(
{"category": ["a", "b", "c", "d", "e", "f"], "value": [4, 6, 10, 3, 7, 8]}
)
base = alt.Chart(source).encode(
theta=alt.Theta("value:Q").stack(True),
color=alt.Color("category:N").legend(None),
)
pie = base.mark_arc(outerRadius=120)
text = base.mark_text(radius=140, size=20).encode(
text="category:N"
)
pie + text
|
