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.. currentmodule:: altair
.. _user-guide-text-marks:
Text
~~~~~~
``text`` mark represents each data point with a text instead of a point.
Text Mark Properties
--------------------
.. altair-plot::
:hide-code:
:div_class: properties-example
import altair as alt
import pandas as pd
angle_slider = alt.binding_range(min=-180, max=180, step=1)
angle_var = alt.param(bind=angle_slider, value=0, name="angle")
dx_slider = alt.binding_range(min=-20, max=20, step=1)
dx_var = alt.param(bind=dx_slider, value=5, name="dx")
dy_slider = alt.binding_range(min=-20, max=20, step=1)
dy_var = alt.param(bind=dy_slider, value=0, name="dy")
xOffset_slider = alt.binding_range(min=-20, max=20, step=1)
xOffset_var = alt.param(bind=xOffset_slider, value=0, name="xOffset")
yOffset_slider = alt.binding_range(min=-20, max=20, step=1)
yOffset_var = alt.param(bind=yOffset_slider, value=0, name="yOffset")
fontSize_slider = alt.binding_range(min=1, max=36, step=1)
fontSize_var = alt.param(bind=fontSize_slider, value=14, name="fontSize")
limit_slider = alt.binding_range(min=0, max=150, step=1)
limit_var = alt.param(bind=limit_slider, value=0, name="limit")
align_select = alt.binding_select(options=["left", "center", "right"])
align_var = alt.param(bind=align_select, value="left", name="align")
baseline_select = alt.binding_select(options=["alphabetic", "top", "middle", "bottom"])
baseline_var = alt.param(bind=baseline_select, value="midle", name="baseline")
font_select = alt.binding_select(options=["sans-serif", "serif", "monospace"])
font_var = alt.param(bind=font_select, value="sans-serif", name="font")
fontWeight_select = alt.binding_select(options=["normal", "bold"])
fontWeight_var = alt.param(bind=fontWeight_select, value="normal", name="fontWeight")
fontStyle_select = alt.binding_select(options=["normal", "italic"])
fontStyle_var = alt.param(bind=fontStyle_select, value="normal", name="fontStyle")
source = pd.DataFrame(
{
"a": [30, 25, 70],
"b": [28, 65, 43],
"label": ["Andy", "Brian", "Charlie"],
}
)
base = alt.Chart(source).encode(
x=alt.X("a:Q").axis(labelAngle=0).scale(domain=[0, 100]),
y=alt.Y("b:Q").scale(domain=[0, 100]),
)
pts = base.mark_point()
text = base.mark_text(
dx=dx_var,
dy=dy_var,
xOffset=xOffset_var,
yOffset=yOffset_var,
angle=angle_var,
align=align_var,
baseline=baseline_var,
font=font_var,
fontSize=fontSize_var,
fontStyle=fontStyle_var,
fontWeight=fontWeight_var,
limit=limit_var,
).encode(text="label:N")
(pts + text).add_params(
dx_var,
dy_var,
xOffset_var,
yOffset_var,
angle_var,
align_var,
baseline_var,
font_var,
fontSize_var,
fontStyle_var,
fontWeight_var,
limit_var,
)
A ``text`` mark definition can contain any :ref:`standard mark properties <mark-properties>`
and the following special properties:
.. altair-object-table:: altair.MarkDef
:properties: angle align baseline dir dx dy ellipsis font fontSize fontStyle fontWeight limit lineHeight radius text theta
Examples
--------
Text Table Heatmap
^^^^^^^^^^^^^^^^^^
.. altair-plot::
import altair as alt
from vega_datasets import data
source = data.cars()
base = alt.Chart(source).transform_aggregate(
num_cars="count()",
groupby=["Origin", "Cylinders"],
).encode(
alt.X("Cylinders:O").scale(paddingInner=0),
alt.Y("Origin:O").scale(paddingInner=0),
)
heatmap = base.mark_rect().encode(
alt.Color("num_cars:Q")
.scale(scheme="viridis")
.legend(direction="horizontal")
)
text = base.mark_text(baseline="middle").encode(
text="num_cars:Q",
color=alt.condition(
alt.datum.num_cars > 100,
alt.value("black"),
alt.value("white"),
),
)
heatmap + text
Labels
^^^^^^
You can also use ``text`` marks as labels for other marks and set offset (``dx`` or ``dy``), ``align``, and ``baseline`` properties of the mark definition.
.. altair-plot::
import altair as alt
import pandas as pd
source = pd.DataFrame({
"a": ["A", "B", "C"],
"b": [28, 55, 43]
})
bar = alt.Chart(source).mark_bar().encode(
y="a:N",
x=alt.X("b:Q").scale(domain=[0, 60])
)
text = bar.mark_text(
align="left",
baseline="middle",
dx=3
).encode(text="b")
bar + text
Scatter Plot with Text
^^^^^^^^^^^^^^^^^^^^^^
Mapping a field to ``text`` channel of text mark sets the mark’s text value. For example, we can make a colored scatter plot with text marks showing the initial character of its origin, instead of ``point`` marks.
.. altair-plot::
import altair as alt
from vega_datasets import data
from altair import datum
source = data.cars()
alt.Chart(source).mark_text().encode(
x="Horsepower:Q",
y="Miles_per_Gallon:Q",
color="Origin:N",
text="Origin[0]:N",
)
Geo Text
^^^^^^^^
By mapping geographic coordinate data to ``longitude`` and ``latitude`` channels of a corresponding projection, we can show text at accurate locations. The example below shows the name of every US state capital at the location of the capital.
.. altair-plot::
import altair as alt
from vega_datasets import data
states = alt.topo_feature(data.us_10m.url, feature="states")
source = data.us_state_capitals()
background = alt.Chart(states).mark_geoshape(
fill="lightgray",
stroke="white",
).properties(
width=750,
height=500,
).project("albersUsa")
line = alt.Chart(source).mark_text(dy=-10).encode(
latitude="lat:Q",
longitude="lon:Q",
text="city:N"
)
point = alt.Chart(source).mark_circle().encode(
latitude="lat:Q",
longitude="lon:Q",
color=alt.value("orange"),
)
background + line + point
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