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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
chart = alt.Chart(source).transform_filter(
alt.datum.symbol != "IBM" # A reducation of the dataset to clarify our example. Not required.
).encode(
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='max(date):T',
y=alt.Y('price:Q').aggregate(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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