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import numpy as np
from .cube_utils import iterator_strategy
from .np_compat import allbadtonan
from .utils import ProgressBar
"""
Functions to compute moment maps in a variety of ways
"""
def _moment_shp(cube, axis):
"""
Return the shape of the moment map
Parameters
-----------
cube : SpectralCube
The cube to collapse
axis : int
The axis to collapse along (numpy convention)
Returns
-------
ny, nx
"""
return cube.shape[:axis] + cube.shape[axis + 1:]
def _slice0(cube, axis):
"""
0th moment along an axis, calculated slicewise
Parameters
----------
cube : SpectralCube
axis : int
Returns
-------
moment0 : array
"""
shp = _moment_shp(cube, axis)
result = np.zeros(shp)
view = [slice(None)] * 3
valid = np.zeros(shp, dtype=bool)
for i in range(cube.shape[axis]):
view[axis] = i
plane = cube._get_filled_data(fill=np.nan, view=tuple(view))
valid |= np.isfinite(plane)
result += np.nan_to_num(plane) * cube._pix_size_slice(axis)
result[~valid] = np.nan
return result
def _slice1(cube, axis):
"""
1st moment along an axis, calculated slicewise
Parameters
----------
cube : SpectralCube
axis : int
Returns
-------
moment1 : array
"""
shp = _moment_shp(cube, axis)
result = np.zeros(shp)
view = [slice(None)] * 3
pix_size = cube._pix_size_slice(axis)
pix_cen = cube._pix_cen()[axis]
weights = np.zeros(shp)
for i in range(cube.shape[axis]):
view[axis] = i
plane = cube._get_filled_data(fill=0, view=tuple(view))
result += (plane *
pix_cen[tuple(view)] *
pix_size)
weights += plane * pix_size
return result / weights
def moment_slicewise(cube, order, axis, progressbar=False):
"""
Compute moments by accumulating the result 1 slice at a time
"""
if order == 0:
return _slice0(cube, axis)
if order == 1:
return _slice1(cube, axis)
shp = _moment_shp(cube, axis)
result = np.zeros(shp)
view = [slice(None)] * 3
pix_size = cube._pix_size_slice(axis)
pix_cen = cube._pix_cen()[axis]
weights = np.zeros(shp)
# would be nice to get mom1 and momn in single pass over data
# possible for mom2, not sure about general case
mom1 = _slice1(cube, axis)
if progressbar:
progressbar = ProgressBar(cube.shape[axis], desc='Moment raywise: ')
pbu = progressbar.update
else:
pbu = lambda: True
for i in range(cube.shape[axis]):
view[axis] = i
plane = cube._get_filled_data(fill=0, view=tuple(view))
result += (plane *
(pix_cen[tuple(view)] - mom1) ** order *
pix_size)
weights += plane * pix_size
pbu()
return (result / weights)
def moment_raywise(cube, order, axis, progressbar=False):
"""
Compute moments by accumulating the answer one ray at a time
"""
shp = _moment_shp(cube, axis)
out = np.zeros(shp) * np.nan
pix_cen = cube._pix_cen()[axis]
pix_size = cube._pix_size_slice(axis)
if progressbar:
progressbar = ProgressBar(out.size, desc='Moment raywise: ')
pbu = progressbar.update
else:
pbu = lambda: True
for x, y, slc in cube._iter_rays(axis):
# the intensity, i.e. the weights
include = cube._mask.include(data=cube._data, wcs=cube._wcs, view=slc,
wcs_tolerance=cube._wcs_tolerance)
if not include.any():
continue
data = cube.flattened(slc).value * pix_size
if order == 0:
out[x, y] = data.sum()
continue
order1 = (data * pix_cen[slc][include]).sum() / data.sum()
if order == 1:
out[x, y] = order1
continue
ordern = (data * (pix_cen[slc][include] - order1) ** order).sum()
ordern /= data.sum()
out[x, y] = ordern
pbu()
return out
def moment_cubewise(cube, order, axis):
"""
Compute the moments by working with the entire data at once
"""
pix_cen = cube._pix_cen()[axis]
data = cube._get_filled_data() * cube._pix_size_slice(axis)
if order == 0:
return allbadtonan(np.nansum)(data, axis=axis)
if order == 1:
return (np.nansum(data * pix_cen, axis=axis) /
np.nansum(data, axis=axis))
else:
mom1 = moment_cubewise(cube, 1, axis)
# insert an axis so it broadcasts properly
shp = list(_moment_shp(cube, axis))
shp.insert(axis, 1)
mom1 = mom1.reshape(shp)
return (np.nansum(data * (pix_cen - mom1) ** order, axis=axis) /
np.nansum(data, axis=axis))
def moment_auto(cube, order, axis):
"""
Build a moment map, choosing a strategy to balance speed and memory.
"""
strategy = dict(cube=moment_cubewise, ray=moment_raywise,
slice=moment_slicewise)
return strategy[iterator_strategy(cube, axis)](cube, order, axis)
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