nbodykit.source.catalog.fkp¶

Classes

class nbodykit.source.catalog.fkp.FKPCatalog(data, randoms, BoxSize=None, BoxPad=0.02, use_cache=True)[source]¶

An interface for simultaneous modeling of a data CatalogSource and a randoms CatalogSource, in the spirit of Feldman, Kaiser, and Peacock, 1994.

This main functionality of this class is:

• provide a uniform interface to accessing columns from the data CatalogSource and randoms CatalogSource, using column names prefixed with “data/” or “randoms/”
• compute the shared BoxSize of the source, by finding the maximum Cartesian extent of the randoms
• provide an interface to a mesh object, which knows how to paint the FKP density field from the data and randoms

Parameters:

data (CatalogSource) – the CatalogSource of particles representing the data catalog randoms (CatalogSource) – the CatalogSource of particles representing the randoms catalog BoxSize (float, 3-vector, optional) – the size of the Cartesian box to use for the unified data and randoms; if not provided, the maximum Cartesian extent of the randoms defines the box BoxPad (float, 3-vector, optional) – optionally apply this additional buffer to the extent of the Cartesian box use_cache (bool, optional) – if True, use the built-in dask cache system to cache data, providing significant speed-ups; requires cachey

References

• Feldman, Kaiser, and Peacock, 1994

Attributes

attrs	A dictionary storing relevant meta-data about the CatalogSource.
columns	Columns for individual species can be accessed using a species/ prefix and the column name, i.e., data/Position.
hardcolumns	Hardcolumn of the form species/name
species	List of species names
use_cache	If set to True, use the built-in caching features of dask to cache data in memory.

Methods

compute(*args, **kwargs)	Our version of dask.compute() that computes multiple delayed dask collections at once.
copy()	Return a shallow copy of the object, where each column is a reference of the corresponding column in self.
get_hardcolumn(col)	Construct and return a hard-coded column.
make_column(array)	Utility function to convert an array-like object to a dask.array.Array.
read(columns)	Return the requested columns as dask arrays.
save(output, columns[, datasets, header])	Save the CatalogSource to a bigfile.BigFile.
to_mesh([Nmesh, BoxSize, dtype, interlaced, …])	Convert the FKPCatalog to a mesh, which knows how to “paint” the FKP density field.
view([type])	Return a “view” of the CatalogSource object, with the returned type set by type.

to_mesh(Nmesh=None, BoxSize=None, dtype='f4', interlaced=False, compensated=False, window='cic', fkp_weight='FKPWeight', comp_weight='Weight', nbar='NZ', selection='Selection', position='Position')[source]¶

Convert the FKPCatalog to a mesh, which knows how to “paint” the FKP density field.

Additional keywords to the to_mesh() function include the FKP weight column, completeness weight column, and the column specifying the number density as a function of redshift.

Parameters:

Nmesh (int, 3-vector, optional) – the number of cells per box side; if not specified in attrs, this must be provided BoxSize (float, 3-vector, optional) – the size of the box; if provided, this will use the default value in attrs dtype (str, dtype, optional) – the data type of the mesh when painting interlaced (bool, optional) – whether to use interlacing to reduce aliasing when painting the particles on the mesh compensated (bool, optional) – whether to apply a Fourier-space transfer function to account for the effects of the gridding + aliasing window (str, optional) – the string name of the window to use when interpolating the particles to the mesh; see pmesh.window.methods for choices fkp_weight (str, optional) – the name of the column in the source specifying the FKP weight; this weight is applied to the FKP density field: n_data - alpha*n_randoms comp_weight (str, optional) – the name of the column in the source specifying the completeness weight; this weight is applied to the individual fields, either n_data or n_random selection (str, optional) – the name of the column used to select a subset of the source when painting nbar (str, optional) – the name of the column specifying the number density as a function of redshift position (str, optional) – the name of the column that specifies the position data of the objects in the catalog