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"""
Seattle Weather Interactive
===========================
This chart provides an interactive exploration of Seattle weather over the
course of the year. It includes a one-axis brush selection to easily
see the distribution of weather types in a particular date range.
"""
# category: case studies
import altair as alt
from vega_datasets import data
source = data.seattle_weather()
scale = alt.Scale(domain=['sun', 'fog', 'drizzle', 'rain', 'snow'],
range=['#e7ba52', '#a7a7a7', '#aec7e8', '#1f77b4', '#9467bd'])
color = alt.Color('weather:N', scale=scale)
# We create two selections:
# - a brush that is active on the top panel
# - a multi-click that is active on the bottom panel
brush = alt.selection_interval(encodings=['x'])
click = alt.selection_multi(encodings=['color'])
# Top panel is scatter plot of temperature vs time
points = alt.Chart().mark_point().encode(
alt.X('monthdate(date):T', title='Date'),
alt.Y('temp_max:Q',
title='Maximum Daily Temperature (C)',
scale=alt.Scale(domain=[-5, 40])
),
color=alt.condition(brush, color, alt.value('lightgray')),
size=alt.Size('precipitation:Q', scale=alt.Scale(range=[5, 200]))
).properties(
width=550,
height=300
).add_selection(
brush
).transform_filter(
click
)
# Bottom panel is a bar chart of weather type
bars = alt.Chart().mark_bar().encode(
x='count()',
y='weather:N',
color=alt.condition(click, color, alt.value('lightgray')),
).transform_filter(
brush
).properties(
width=550,
).add_selection(
click
)
alt.vconcat(
points,
bars,
data=source,
title="Seattle Weather: 2012-2015"
)
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