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"""
Line Chart with Last Value Labeled
----------------------------------
This chart shows a line chart with a label annotating the final value
"""
# category: line charts
import altair as alt
from vega_datasets import data
# Import example data
source = data.stocks()
# Create a common chart object
# Use `transform_filter` to reduce the dataset to clarify our example. Not required.
chart = (
alt.Chart(source)
.transform_filter(alt.datum.symbol != "IBM")
.encode(color=alt.Color("symbol", legend=None))
)
# Draw the line
line = chart.mark_line().encode(x="date:T", y="price:Q")
# Use the `argmax` aggregate to limit the dataset to the final value
label = chart.encode(
x=alt.X("max(date):T"),
y=alt.Y("price:Q", aggregate=alt.ArgmaxDef(argmax="date")),
text="symbol",
)
# Create a text label
text = label.mark_text(align="left", dx=4)
# Create a circle annotation
circle = label.mark_circle()
# Draw the chart with all the layers combined
line + circle + text
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