Classes
Base3PCF (source, poles, edges, required_cols) 
Base class for implementing common 3PCF calculations. 
SimulationBox3PCF (source, poles, edges[, …]) 
Compute the multipoles of the isotropic, threepoint correlation function in configuration space for data in a simulation box. 
SurveyData3PCF (source, poles, edges, cosmo) 
Compute the multipoles of the isotropic, threepoint correlation function in configuration space for observational survey data. 
YlmCache (ells, comm) 
A class to compute spherical harmonics \(Y_{lm}\) up to a specified maximum \(\ell\). 
nbodykit.algorithms.threeptcf.
Base3PCF
(source, poles, edges, required_cols, BoxSize=None, periodic=None)[source]¶Base class for implementing common 3PCF calculations.
Users should use SimulationBox3PCF
or SurveyData3PCF
.
Methods
load (filename[, comm]) 
Load a result from filename that has been saved to disk with save() . 
save (output) 
Save the poles result to a JSON file with name output . 
nbodykit.algorithms.threeptcf.
SimulationBox3PCF
(source, poles, edges, BoxSize=None, periodic=True, weight='Weight')[source]¶Compute the multipoles of the isotropic, threepoint correlation function in configuration space for data in a simulation box.
This uses the algorithm of Slepian and Eisenstein, 2015 which scales as \(\mathcal{O}(N^2)\), where \(N\) is the number of objects.
Results are computed when the object is inititalized. See the documenation
of run()
for the attributes storing the results.
Note
The algorithm expects the positions of objects in a simulation box to
be the Cartesian x
, y
, and z
vectors. For survey data,
in the form of right ascension, declination, and
redshift, see SurveyData3PCF
.
Parameters: 


References
Slepian and Eisenstein, MNRAS 454, 41424158 (2015)
Methods
load (filename[, comm]) 
Load a result from filename that has been saved to disk with save() . 
run ([pedantic]) 
Compute the threepoint CF multipoles. 
save (output) 
Save the poles result to a JSON file with name output . 
load
(filename, comm=None)¶Load a result from filename
that has been saved to
disk with save()
.
run
(pedantic=False)[source]¶Compute the threepoint CF multipoles. This attaches the following the attributes to the class:
poles
¶a BinnedStatistic object to hold the multipole results; the
binned statistics stores the multipoles as variables corr_0
,
corr_1
, etc for \(\ell=0,1,\) etc. The coordinates
of the binned statistic are r1
and r2
, which give the
separations between the three objects in CF.
Type:  BinnedStatistic 

nbodykit.algorithms.threeptcf.
SurveyData3PCF
(source, poles, edges, cosmo, domain_factor=4, ra='RA', dec='DEC', redshift='Redshift', weight='Weight')[source]¶Compute the multipoles of the isotropic, threepoint correlation function in configuration space for observational survey data.
This uses the algorithm of Slepian and Eisenstein, 2015 which scales as \(\mathcal{O}(N^2)\), where \(N\) is the number of objects.
Results are computed when the object is inititalized. See the documenation
of run()
for the attributes storing the results.
Note
The algorithm expects the positions of objects from a survey catalog
be the sky coordinates, right ascension and declination, and redshift.
For simulation box data in Cartesian coordinates, see
SimulationBox3PCF
.
Warning
The right ascension and declination columns should be specified in degrees.
Parameters: 


References
Slepian and Eisenstein, MNRAS 454, 41424158 (2015)
Methods
load (filename[, comm]) 
Load a result from filename that has been saved to disk with save() . 
run () 
Compute the threepoint CF multipoles. 
save (output) 
Save the poles result to a JSON file with name output . 
load
(filename, comm=None)¶Load a result from filename
that has been saved to
disk with save()
.
run
()[source]¶Compute the threepoint CF multipoles. This attaches the following the attributes to the class:
poles
¶a BinnedStatistic object to hold the multipole results; the
binned statistics stores the multipoles as variables corr_0
,
corr_1
, etc for \(\ell=0,1,\) etc. The coordinates
of the binned statistic are r1
and r2
, which give the
separations between the three objects in CF.
Type:  BinnedStatistic 

nbodykit.algorithms.threeptcf.
YlmCache
(ells, comm)[source]¶A class to compute spherical harmonics \(Y_{lm}\) up to a specified maximum \(\ell\).
During calculation, the necessary power of Cartesian unit vectors are cached in memory to avoid repeated calculations for separate harmonics.
Methods
__call__ (xpyhat, zhat) 
Return a dictionary holding Ylm for each (l,m) combination required 