def timeline(sensor_id):
"""
Returns all measurements for one particular sensor.
"""
timeline = db.dict_query('''SELECT time, temperature FROM measurements
WHERE sensor_id = ? ORDER BY time''', [sensor_id])
return timeline
def population_density(year=None):
if year is None:
rows = db.query("""SELECT MAX(pop_year) FROM cantons_pop""")
year = rows.fetchone()[0]
pop_dens = db.dict_query("""SELECT cantons_pop.abbr, pop_year,
pop, pop / area_ha AS pop_dens
FROM cantons_pop JOIN cantons ON cantons_pop.abbr = cantons.abbr
WHERE pop_year = ?""", (year,))
# Note that in a Sqlite query the placeholder for a variable value is ?
# (it would be %s in Postgres)
return pop_dens
def sensors():
"""
Returns the ID, name, elevation and point geometry of all sensors.
"""
sensors = db.dict_query('SELECT id, geometry, name, elevation FROM sensors')
# Sensors are in WGS84 (EPSG:4326) in the database.
# We need to transform the coordinates to Google Mercator (EPSG:900913),
# which is the SRS of the OpenLayers map
for c in sensors:
sensors[c]['geometry'].set_srid(4326)
sensors[c]['geometry'].transform(900913)
return sensors
def measurements(time=None, time_window=30):
"""
Returns all available measurements at a given time (None means latest
measurements), plus/minus a time window (30 minutes by default).
"""
if time is None: # Query the database to get time of latest measurement
time = db.query('SELECT MAX(time) FROM measurements').fetchone()[0]
from_time = time - timedelta(minutes=time_window)
to_time = time + timedelta(minutes=time_window)
measurements = db.dict_query('''SELECT sensor_id, time,
AVG(temperature) AS t FROM measurements WHERE time > ? AND time < ?
GROUP BY sensor_id''', [from_time, to_time])
return measurements
def cantons():
cantons = db.dict_query("""SELECT abbr, the_geom FROM cantons""")
return cantons
