Add a visualization script

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Lucas Verney 2017-08-28 14:20:00 +02:00
parent 93aa2e8464
commit 4e4c3eadf7
1 changed files with 182 additions and 0 deletions

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visu.py Executable file
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#!/usr/bin/env python3
# coding: utf-8
"""
Visualisation of Velib data
Note: This does not take into account the stations events.
"""
from __future__ import division
import datetime
import logging
import os
import pickle
import sqlite3
import matplotlib
matplotlib.use('AGG') # Use non-interactive backend
import matplotlib.pyplot as plt
import progressbar
import smopy
from scipy.spatial import Voronoi, voronoi_plot_2d
def get_hue(percentage):
"""
Convert a percentage to a hue,
to map a percentage to a color
in the green - yellow - orange - red scale.
"""
value = percentage / 100.0
hue = (1 - value) * 120
return hue / 360.0
progressbar.streams.wrap_stderr()
logging.basicConfig(level=logging.INFO)
# Ensure out folder exists
if not os.path.isdir('out'):
logging.info('Creating out folder…')
os.mkdir('out')
# Load all stations from the database
logging.info('Loading all stations from the database…')
conn = sqlite3.connect("data.db")
c = conn.cursor()
stations = c.execute(
"SELECT id, latitude, longitude, bike_stands, name FROM stations"
).fetchall()
stations = [
station
for station in stations
if station[1] > 0 and station[2] > 0
] # Filter out invalid stations
logging.info('Loaded %d stations from database.', len(stations))
# Set tiles server and params
smopy.TILE_SERVER = "http://a.tile.stamen.com/toner-lite/{z}/{x}/{y}@2x.png"
smopy.TILE_SIZE = 512
smopy.MAXTILES = 25
# Compute map bounds as the extreme stations
lower_left_corner = (
min(station[1] for station in stations),
min(station[2] for station in stations)
)
upper_right_corner = (
max(station[1] for station in stations),
max(station[2] for station in stations)
)
# Get the tiles
# Note: Force zoom to 12 to still have city names (and not e.g. street names)
logging.info('Fetching tiles between %s and %s' % (lower_left_corner, upper_right_corner))
map = smopy.Map(lower_left_corner + upper_right_corner, z=12)
# Compute the station points coordinates
# (converting from lat/lng to pixels for matplotlib)
station_points = [
map.to_pixels(station[1], station[2]) for station in stations
]
# Compute Voronoi diagram of available stations
logging.info('Computing Voronoi diagram of the stations…')
vor = Voronoi(station_points)
# This is a mapping between ID of stations and
# matching Voronoi tile, for faster reuse
vor_regions = {}
for point_index, region_index in enumerate(vor.point_region):
station_id = stations[point_index][0]
region = vor.regions[region_index]
if -1 in region: # Discard regions with points out of bounds
continue
vor_regions[station_id] = {
"polygon": [vor.vertices[i] for i in region], # Polygon, as a list of points
"mpl_surface": None # Will store the drawn matplotlib surface (to update it easily)
}
# Dumping Voronoi diagram
with open('out/voronoi.dat', 'wb') as fh:
pickle.dump(vor_regions, fh)
logging.info('Dumped Voronoi diagram to out/voronoi.dat')
# Plotting
logging.info('Initializing Matplotlib figure…')
map_img = map.to_pil()
aspect_ratio = map_img.size[1] / map_img.size[0]
# Create a matplotlib figure
fig, ax = plt.subplots(figsize=(8, 8 * aspect_ratio))
ax.set_xticks([])
ax.set_yticks([])
ax.grid(False)
# Compute bounds
# Note: This is necessary because OSM tiles have some spatial
# extension and might expand farther than the requested bounds.
x_min, y_min = map.to_pixels(lower_left_corner)
x_max, y_max = map.to_pixels(upper_right_corner)
ax.set_xlim(x_min, x_max)
ax.set_ylim(y_min, y_max)
ax.imshow(map_img)
# Initialize Voronoi Matplotlib surfaces to grey
logging.info('Initializing Voronoi surfaces in the figure…')
for station_id, region in vor_regions.items():
vor_regions[station_id]["mpl_surface"] = ax.fill(
alpha=0.25,
*zip(*region["polygon"]),
color="#9e9e9e"
)[0]
# Get time steps
logging.info('Loading time steps from the database.')
time_data = c.execute(
"SELECT DISTINCT updated FROM stationsstats WHERE updated ORDER BY updated ASC"
)
last_t = None
timesteps = 5 * 60 * 1000 # 5 mins timesteps between each frames
logging.info('Plotting graphs!')
bar = progressbar.ProgressBar()
for t, in bar(time_data):
if last_t is None:
# Initialize last_t
last_t = t
# For each available station, retrieve its time data
c2 = conn.cursor()
stations_stats = c2.execute(
"SELECT station_id, available_bikes FROM stationsstats WHERE updated=?",
(t,)
)
for station_data in stations_stats:
# Compute the available bikes percentages for this station over time
bike_stands = next(station[3] for station in stations if station[0] == station_data[0])
percentage = station_data[1] / bike_stands * 100.0
if percentage > 100:
# TODO: This happens when a station has changed size inside the
# dataset. Should be handled better.
percentage = 100
# Plot "regions of influence" of the velib stations (Voronoi regions)
try:
region = vor_regions[station_data[0]]
region["mpl_surface"].set_color(matplotlib.colors.hsv_to_rgb([get_hue(percentage), 1.0, 1.0]))
except KeyError:
logging.warn('Unknown Voronoi region for station %d.', station_data[0])
# Output frame if necessary
if t >= last_t + timesteps:
ax.set_title(datetime.datetime.fromtimestamp(t // 1000).strftime('%d/%m/%Y %H:%M'))
fig.tight_layout()
fig.savefig('out/%d.png' % t)
last_t = t
# Output last frame
fig.tight_layout()
fig.savefig('out/%d.png' % t)