def _centroids_creation(firms, centr_res_factor):
""" Compute centroids for the firms dataset.
The number of centroids is defined according to the data resolution.
Parameters:
firms (dataframe): dataset obtained from FIRMS data
centr_res_factor (float): the factor applied to voluntarly decrease/increase
the centroids resolution
Returns:
centroids (Centroids)
res_data (float): data resolution (km)
"""
LOGGER.info('Defining the resolution of the centroids.')
# Resolution of the centroids depends on the data origin.
# Resolution in km.
if 'instrument' in firms.columns:
if firms['instrument'].any() == 'MODIS':
res_data = 1.0
else:
res_data = 0.375 # For VIIRS data
else:
res_data = RES_DATA # For undefined data origin, defined by user
LOGGER.info('Computing centroids.')
centroids = Centroids()
dlat_km = abs(firms['latitude'].min() - firms['latitude'].max()) * ONE_LAT_KM
dlon_km = abs(firms['longitude'].min() - firms['longitude'].max()) * ONE_LAT_KM* \
np.cos(np.radians((abs(firms['latitude'].min() - firms['latitude'].max()))/2))
nb_centr_lat = int(dlat_km/res_data * centr_res_factor)
nb_centr_lon = int(dlon_km/res_data * centr_res_factor)
coord = (np.mgrid[firms['latitude'].min() : firms['latitude'].max() : \
complex(0, nb_centr_lat), firms['longitude'].min() : firms['longitude'].max() : \
complex(0, nb_centr_lon)]).reshape(2, nb_centr_lat*nb_centr_lon).transpose()
centroids.set_lat_lon(coord[:, 0], coord[:, 1])
# centroids.set_raster_from_pnt_bounds((firms['longitude'].min(),
# firms['latitude'].min(), firms['longitude'].max(), firms['latitude'].max()),
# res=res_data/centr_res_factor) ---> propagation works?
# Calculate the area attributed to each centroid
centroids.set_area_approx()
# Calculate if the centroids is on land or not
centroids.set_on_land()
# Calculate to distance to coast
centroids.set_dist_coast()
# Create on land grid
centroids.land = centroids.on_land.reshape((nb_centr_lat, nb_centr_lon)).astype(int)
centroids.nb_centr_lat = nb_centr_lat
centroids.nb_centr_lon = nb_centr_lon
centroids.empty_geometry_points()
return centroids, res_data
