Interactive Weather Chart with Altair

Creating an interactive chart that combines maximum daily temperature, percipitation, date, type of weather and allows interactive filtering.
python
altair
visualisation
Published

November 15, 2022

Code 
import altair as alt
from vega_datasets import data
import pandas as pd

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',
          scale=alt.Scale(domain=[pd.Timestamp(2012, 1, 1), pd.Timestamp(2012, 12, 31)])),
    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"
)