nbodykit.algorithms.pair_counters.mocksurvey¶
Classes
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Count (weighted) pairs of objects from a survey data catalog as a function of \(r\), \((r,\mu)\), \((r_p, \pi)\), or \(\theta\) using the |
- class nbodykit.algorithms.pair_counters.mocksurvey.SurveyDataPairCount(mode, first, edges, cosmo=None, second=None, Nmu=None, pimax=None, ra='RA', dec='DEC', redshift='Redshift', weight='Weight', show_progress=False, domain_factor=4, **config)[source]¶
Count (weighted) pairs of objects from a survey data catalog as a function of \(r\), \((r,\mu)\), \((r_p, \pi)\), or \(\theta\) using the
Corrfunc
package.See the Notes below for the allowed coordinate dimensions.
The default weighting scheme uses the product of the weights for each object in a pair.
Results are computed when the class is inititalized. See the documenation of
run()
for the attributes storing the results.Note
The algorithm expects the positions of particles from a survey catalog be the sky coordinates, right ascension and declination, and redshift. To compute pair counts in a simulation box using Cartesian coordinates, see
SimulationBoxPairCount
.Warning
The right ascension and declination columns should be specified in degrees.
- Parameters
mode ('1d', '2d', 'projected', 'angular') – compute pair counts as a function of the specified coordinate basis; see the Notes section below for specifics
first (CatalogSource) – the first source of particles, providing the ‘Position’ column
edges (array_like) – the separation bin edges along the first coordinate dimension; depending on
mode
, the options are \(r\), \(r_p\), or \(\theta\). Expected units for distances are \(\mathrm{Mpc}/h\) and degrees for angles. Length of nbins+1cosmo (
Cosmology
, optional) – the cosmology instance used to convert redshift into comoving distance; this is required for all cases exceptmode='angular'
second (CatalogSource, optional) – the second source of particles to cross-correlate
Nmu (int, optional) – the number of \(\mu\) bins, ranging from 0 to 1; requred if
mode='2d'
pimax (float, optional) – The maximum separation along the line-of-sight when
mode='projected'
. Distances along the \(\pi\) direction are binned with unit depth. For instance, ifpimax=40
, then 40 bins will be created along the \(\pi\) direction.ra (str, optional) – the name of the column in the source specifying the right ascension coordinates in units of degrees; default is ‘RA’
dec (str, optional) – the name of the column in the source specifying the declination coordinates; default is ‘DEC’
redshift (str, optional) – the name of the column in the source specifying the redshift coordinates; default is ‘Redshift’
weight (str, optional) – the name of the column in the source specifying the object weights
show_progress (bool, optional) – if
True
, perform the pair counting calculation in 10 iterations, logging the progress after each iteration; this is useful for understanding the scaling of the codedomain_factor (int, optional) – the integer value by which to oversubscribe the domain decomposition mesh before balancing loads; this number can affect the distribution of loads on the ranks – an optimal value will lead to balanced loads
**config (key/value pairs) – additional keywords to pass to the
Corrfunc
function
Notes
This class can compute pair counts using several different coordinate choices, based on the value of the input argument
mode
. The choices are:mode='1d'
: compute pairs as a function of the 3D separation \(r\)mode='2d'
: compute pairs as a function of the 3D separation \(r\) and the cosine of the angle to the line-of-sight, \(\mu\)mode='projected'
: compute pairs as a function of distance perpendicular and parallel to the line-of-sight, \(r_p\) and \(\pi\)mode='angular'
: compute pairs as a function of angle on the sky, \(\theta\)
Methods
load
(output[, comm])Load a result has been saved to disk with
save()
.run
()Calculate the pair counts of a survey data catalog.
save
(output)Save result as a JSON file with name
output
- run()[source]¶
Calculate the pair counts of a survey data catalog. This adds the following attribute:
self.pairs.attrs[‘total_wnpairs’]: The total of wnpairs.
- pairs¶
a BinnedStatistic object holding the pair count results. The coordinate grid will be
(r,)
,(r,mu)
,(rp, pi)
, or(theta,)
whenmode
is ‘1d’, ‘2d’, ‘projected’, ‘angular’, respectively.The BinnedStatistic stores the following variables:
r
,rp
, ortheta
: the mean separation value in the binnpairs
: the number of pairs in the binwnpairs
: the weighted npairs in the bin; each pair contributes the product of the individual weight values
- Type
- save(output)¶
Save result as a JSON file with name
output