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chart_layers.py
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chart_layers.py
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import altair as alt
import pandas as pd
# Colours used on chart.
colour_night = "#d1d3ea" # lavender
colour_best = "#30a639" # green
colour_worst = "#c0141b" # red
colour_water = "#bcdaf2" # blue
colour_days = "#767676" # grey
time_zone = "Australia/Brisbane"
time_format = "%I:%M %p on %a %d %b"
def darkness(sun):
"""
Rectangle chart of dark periods between daylight periods.
"""
# Get dusk on one day and dawn on the next.
night = pd.DataFrame().reindex_like(sun)
night['dusk'] = sun['dusk']
night['dawn'] = sun['dawn'].shift(-1)
night = night[night['dawn'].notnull()]
domain = [night['dusk'].min(), night['dawn'].max()]
return alt.Chart(night).mark_rect(opacity=0.6, color=colour_night, clip=True).encode(
x=alt.X(
"dusk:T",
# Have to convert pd.Timestamp to alt.DateTime for temporal domain.
scale=alt.Scale(domain=[convert_dt(t) for t in domain]),
),
x2="dawn:T",
tooltip=[
alt.Tooltip("dusk", format=time_format),
alt.Tooltip("dawn", format=time_format),
]
)
def convert_dt(dt):
return alt.DateTime(
year=dt.year,
month=dt.month,
date=dt.day,
hours=dt.hour,
minutes=dt.minute,
)
def days(sun):
"""
Show label for each day on chart at noon.
"""
return alt.Chart(sun[1:-1]).mark_text(
clip=False,
color=colour_days,
dy=-12,
fontSize=16,
).encode(
x="noon:T",
y=alt.value(0),
text=alt.Text("noon:T", format="%a %d %b"),
)
def heights(tides):
"""
Area chart of tide heights.
"""
return alt.Chart(tides).mark_area(
clip=True,
line=False,
color=colour_water,
opacity=0.5,
).encode(
x=alt.X(
"time:T",
title=None,
axis=alt.Axis(grid=False, ticks=True, labelAngle=-45),
),
y=alt.Y(
"height:Q",
title="Tide Height (m)",
axis=alt.Axis(grid=True, tickCount=5),
scale=alt.Scale(zero=True),
),
tooltip=[
alt.Tooltip("time", format=time_format),
alt.Tooltip("height", format=".1f"),
],
)
def curve(tides, safe):
"""
Line chart of tide height coloured by safety.
"""
# Hide parts of line that are safe/unsafe.
line = tides[['time', 'height', 'safe']].copy()
hide = ~line['safe'] if safe else line['safe']
line.loc[hide, 'height'] = None
# Show coloured parts of line that are not hidden.
return alt.Chart(line).mark_line(
clip=True,
color=colour_best if safe else colour_worst,
).encode(
x="time:T",
y="height:Q",
tooltip=[
alt.Tooltip("time", format=time_format),
alt.Tooltip("height", format=".1f"),
],
)
def periods(low, high):
"""
Labels giving safe driving periods.
"""
time_only = "%I:%M%p"
safer = low[low['earliest'].notnull() & low['latest'].notnull()].copy()
safer['period'] = (
"✓ " + safer['earliest'].dt.strftime(time_only).str.lstrip('0')
+ " - " + safer['latest'].dt.strftime(time_only).str.lstrip('0')
).str.lower()
# Find maximum height to show times above that
# using steps to get positions of text labels.
highest = high['height'].max()
steps = highest * 0.11
# Rank tides by time of day and position labels with the earliest above the latest.
safer['rank'] = safer.groupby('day', as_index=False)['time'].rank()
safer['level'] = highest + (3 - safer['rank']) * steps
return alt.Chart(safer).mark_text(
clip=True,
align="center",
color=colour_best,
fontSize=16,
).encode(
x="noon:T",
# Leave space above safe periods for hints (below).
y=alt.Y("level:Q", scale=alt.Scale(domainMax=highest * 1.4)),
text="period:N",
tooltip=["day", "period"],
)
def hints(sun, label):
"""
Label above safer periods.
"""
return alt.Chart(sun).mark_text(
clip=True,
tooltip=False,
align="center",
baseline="middle",
color=colour_best,
fontSize=12,
dy=20,
).encode(
x="noon:T",
y=alt.value(0),
text=alt.value(label),
)
def crosses(high):
"""
Red crosses under the high tides.
"""
return alt.Chart(high).mark_text(
clip=True,
tooltip=False,
align="center",
color=colour_worst,
dy=20,
fontSize=18,
).encode(
x="time:T",
y="height:Q",
text=alt.value("✕"),
)
def icons(sun):
# FIXME How to position image to avoid clash with chart elements?
return alt.Chart(sun[1:-1]).mark_image(
tooltip=False,
clip=True,
aspect=True,
align="center",
width=50,
).encode(
x="noon:T",
y=alt.value(-200),
url=alt.value("/app/static/beach4wd.png"),
)