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Fix FFTPower to only use positive mu by default #629

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Fix FFTPower to only use positive mu by default #629

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16 changes: 13 additions & 3 deletions nbodykit/algorithms/fftpower.py
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Original file line number Diff line number Diff line change
Expand Up @@ -187,11 +187,15 @@ class FFTPower(FFTBase):
poles : list of int, optional
a list of multipole numbers ``ell`` to compute :math:`P_\ell(k)`
from :math:`P(k,\mu)`
use_negative_mu : bool, optional
set to True if you want ``mu`` bins to range from -1 to 1
else they range from 0 to 1
"""
logger = logging.getLogger('FFTPower')

def __init__(self, first, mode, Nmesh=None, BoxSize=None, second=None,
los=[0, 0, 1], Nmu=5, dk=None, kmin=0., kmax=None, poles=[]):
los=[0, 0, 1], Nmu=5, dk=None, kmin=0., kmax=None, poles=[],
use_negative_mu=False):

# mode is either '1d' or '2d'
if mode not in ['1d', '2d']:
Expand All @@ -213,6 +217,8 @@ def __init__(self, first, mode, Nmesh=None, BoxSize=None, second=None,
self.attrs['los'] = los
self.attrs['Nmu'] = Nmu
self.attrs['poles'] = poles

self.use_negative_mu = use_negative_mu

if dk is None:
dk = 2 * numpy.pi / self.attrs['BoxSize'].min()
Expand Down Expand Up @@ -295,7 +301,11 @@ def run(self):
kedges, kcoords = _find_unique_edges(y3d.x, 2 * numpy.pi / y3d.BoxSize, kmax, y3d.pm.comm)

# project on to the desired basis
muedges = numpy.linspace(-1, 1, self.attrs['Nmu']+1, endpoint=True)
if self.use_negative_mu:
mu_min = -1
else:
mu_min = 0
muedges = numpy.linspace(mu_min, 1, self.attrs['Nmu']+1, endpoint=True)
edges = [kedges, muedges]
coords = [kcoords, None]
result, pole_result = project_to_basis(y3d, edges,
Expand Down Expand Up @@ -762,4 +772,4 @@ def find_unique_local(x, x0):
edges[0] = 0

# fx is the 'true' centers, up to round-off errors.
return edges, fx
return edges, fx