def longitude_slicer(lons, query):
"""
Returns a slice object that will slice out the smallest chunk of lons
that covers the query domain defined by query['domain']['W'] and
query['domain']['E'].
The resulting slice will result in longitudes which increase from west
to east, with a grid delta that is closest to the request grid delta,
query['resolution'].
"""
domain = query['domain']
lons = np.asarray(lons, dtype=np.float32)
if 'grid_delta' in query:
warnings.warn('grid_delta in queries is obsolete, use resolution')
lon_delta = query.get('resolution', None)
slicer = angle_slicer(lons, domain['W'], domain['E'], lon_delta)
# at least one point west of the eastern edge
assert np.any(angles.angle_diff(lons[slicer], domain['E']) <= 0.)
# east of the eastern edge
assert np.any(angles.angle_diff(lons[slicer], domain['E']) >= 0.)
# east of the western edge
assert np.any(angles.angle_diff(lons[slicer], domain['W']) >= 0.)
# west of the western edge
assert np.any(angles.angle_diff(lons[slicer], domain['W']) <= 0.)
return slicer
def bounding_box(fcst, pad=0.1, lon_pad=None, lat_pad=None):
lons = np.unique(fcst['longitude'].values)
lats = np.unique(fcst['latitude'].values)
lon_diffs = angles.angle_diff(lons[:, None], lons)
lat_diffs = angles.angle_diff(lats[:, None], lats)
western_most_ind = np.nonzero(np.all(lon_diffs >= 0., axis=0))[0]
western_most = np.unique(lons[western_most_ind]).item()
eastern_most_ind = np.nonzero(np.all(lon_diffs <= 0., axis=0))[0]
eastern_most = np.unique(lons[eastern_most_ind]).item()
northern_most_ind = np.nonzero(np.all(lat_diffs <= 0., axis=0))[0]
northern_most = np.unique(lats[northern_most_ind]).item()
southern_most_ind = np.nonzero(np.all(lat_diffs >= 0., axis=0))[0]
southern_most = np.unique(lats[southern_most_ind]).item()
# count the number of lons greater than and less than each lon
# and take the difference. The longitude (or pair of lons) that
# minimize this help us determine the median. This allows different
# definitions of longitude.
lon_rel_loc = np.abs(np.sum(lon_diffs >= 0., axis=0) -
np.sum(lon_diffs <= 0., axis=0))
central_lons = lons[lon_rel_loc == np.min(lon_rel_loc)]
# make sure the central two aren't too far apart.
assert np.max(central_lons) - np.min(central_lons) < 90
median_lon = np.median(central_lons)
lat_rel_loc = np.abs(np.sum(lat_diffs >= 0., axis=0) -
np.sum(lat_diffs <= 0., axis=0))
central_lats = lats[lat_rel_loc == np.min(lat_rel_loc)]
median_lat = np.median(central_lats)
width = angles.geographic_distance(western_most, median_lat,
eastern_most, median_lat)
height = angles.geographic_distance(median_lon, northern_most,
median_lon, southern_most)
if lon_pad is None:
lon_pad = pad * np.abs(angles.angle_diff(eastern_most,
western_most))
if lat_pad is None:
lat_pad = pad * np.abs(angles.angle_diff(northern_most,
southern_most))
return {'llcrnrlon': western_most - lon_pad,
'urcrnrlon': eastern_most + lon_pad,
'urcrnrlat': northern_most + lat_pad,
'llcrnrlat': southern_most - lat_pad,
'width': width * (1. + 2 * pad),
'height': height * (1. + 2 * pad),
'lon_0': median_lon,
'lat_0': median_lat}
def angle_slicer(x, low, high, delta=None, tolerance=4):
"""
A function which returns a slicer that will extract all
the values in x that fall between low and high with a prescribed
grid delta.
"""
assert x.ndim == 1
# determine the native grid delta.
diffs = angles.angle_diff(x)
diffs = np.unique(np.round(diffs, tolerance))
# assume angles are equally spaced.
assert diffs.size == 1
native_delta = np.abs(diffs[0])
# round to the nearest native stride but make sure we dont hit zero
delta = delta or native_delta
stride = max(1, int(np.round(delta / native_delta)))
def fully_contained(y):
"""Returns true if the range low/high is contained in y"""
return (np.any(angles.angle_diff(low, y) >= 0) and
np.any(angles.angle_diff(high, y) <= 0))
high_diff = angles.angle_diff(x, high)
low_diff = angles.angle_diff(x, low)
inside_domain = np.logical_and(high_diff <= 0, low_diff >= 0)
# if the edges are in the domain, make sure everything is
# otherwise we will have to use multiple slicers.
if inside_domain[0] and inside_domain[-1]:
assert np.all(inside_domain)
# returns the index which minimizes x conditional on 'cond' being true
def argmin_conditional(x, cond):
x = x.copy()
x[np.logical_not(cond)] = np.nan
return np.nanargmin(x)
# find the indices of the values that fall on or just outside the
# lower and higher limits.
low_ind = argmin_conditional(-low_diff, low_diff <= 0.)
high_ind = argmin_conditional(high_diff, high_diff >= 0.)
# if the angles in x are descending we flip the indices around
if low_ind > high_ind:
high_ind, low_ind = low_ind, high_ind
possible_slicers = [slice(low_ind - i, high_ind - i + 1, stride)
for i in range(stride)]
# we strive to find a slicer that yield the fewest number of point
# that fully contains the domain.
possible_slicers = [s for s in possible_slicers if fully_contained(x[s])]
if not len(possible_slicers):
raise ValueError("Couldn't find a slice that would provide contain "
"the desired domain")
return possible_slicers[0]
def test_angle_diff(self):
pairs = [((180, 180), 0.),
((181, 181), 0.),
((-1, -1), 0.),
((180, -180), 0.),
# note, wrapped values get sent to -180
((180, 0), -180.),
((0, 180), -180.),
((360, 180), -180.),
((361, 181), -180.),
((179, 0), 179.),
((0, 179), -179.),
((360, 181), 179.),
((1, 182), 179.),
((181, 179), 2.),
((179, 181), -2.),
((361, 359), 2.),
((-1, 1.), -2.),
((np.pi - 0.1, 0., False), np.pi - 0.1),
((np.pi - 0.1, -np.pi + 0.1, False), -0.2)]
for args, expected in pairs:
actual = angles.angle_diff(*args)
self.assertAlmostEqual(expected,
actual,
places=6,
msg=("actual: %f "
"expected: %f "
"args: %s"
% (actual, expected,
args)))
def test_maximum_error(self):
from slocum.lib import angles
ds = self.get_data()
scheme = self.get_scheme()
actual = roundtrip(scheme, ds)
diff = angles.angle_diff(ds[scheme.variable_name].values,
actual[scheme.variable_name].values)
self.assertTrue(np.all(np.abs(diff) <= np.pi/16))
def __init__(self, fcst, velocity_variable,
speed_units='knots', ax=None, fig=None,
**kwdargs):
self.variable = velocity_variable
self.speed_units = speed_units
# set the default colormap if needed
kwdargs['cmap'] = kwdargs.get('cmap', velocity_cmap)
# convert the bins to knots
bins = xray.Variable('bins',
velocity_variable.speed_bins.copy(),
{'units': velocity_variable.units})
_, self.bins, _ = units.convert_units(bins, speed_units)
default_norm = plt.cm.colors.BoundaryNorm(self.bins, self.bins.size)
kwdargs['norm'] = kwdargs.get('norm', default_norm)
self.variable = velocity_variable
self.ax, self.fig = utils.axis_figure(ax, fig)
# add the color bar
self.cax = self.fig.add_axes([0.92, 0.05, 0.03, 0.9])
cbar = mpl.colorbar.ColorbarBase(self.cax,
cmap=kwdargs['cmap'],
norm=kwdargs['norm'])
cbar.set_label("Knots")
fcst = self.normalize(fcst)
# use the longitude grid to define the radius of the circles
sorted_lats = np.sort(fcst['latitude'].values)
resol = np.median(angles.angle_diff(sorted_lats[1:],
sorted_lats[:-1]))
# create the map
self.m = utils.get_basemap(fcst, ax=self.ax,
lon_pad=0.75 * resol,
lat_pad = 0.75 * resol)
def create_circle(one_loc):
# determine the circle center
x, y = self.m(one_loc['longitude'].values,
one_loc['latitude'].values)
speeds = one_lonlat[self.variable.speed_name].values
dirs = one_lonlat[self.variable.direction_name].values
orientation = self.variable.direction_orientation
return DirectionCircle(x, y,
speeds=np.atleast_1d(speeds),
directions=np.atleast_1d(dirs),
orientation=orientation,
radius=0.4 * resol,
ax=self.ax, **kwdargs)
self.circles = [[create_circle(one_lonlat)
for lo, one_lonlat in one_lat.groupby('longitude')]
for la, one_lat in fcst.groupby('latitude')]
self.set_title(fcst)
def fully_contained(y):
"""Returns true if the range low/high is contained in y"""
return (np.any(angles.angle_diff(low, y) >= 0) and
np.any(angles.angle_diff(high, y) <= 0))
