nbodykit.cosmology.correlation¶

Functions

`pk_to_xi`(k, Pk[, extrap])	Return a callable function returning the correlation function, as computed from the Fourier transform of the input \(k\) and \(P(k)\) arrays.
`xi_to_pk`(r, xi[, extrap])	Return a callable function returning the power spectrum, as computed from the Fourier transform of the input \(r\) and \(\xi(r)\) arrays.

Classes

CorrelationFunction(power) Evaluate the correlation function by Fourier transforming a power spectrum object, with automatic re-scaling with redshift and sigma8.

class nbodykit.cosmology.correlation.CorrelationFunction(power)[source]¶

Evaluate the correlation function by Fourier transforming a power spectrum object, with automatic re-scaling with redshift and sigma8.

Parameters:	power (callable) – a callable power spectrum that returns the power at a given `k`; this should have `redshift`, `sigma8`, and `cosmo` attributes

Attributes

`attrs`
`cosmo`
`redshift`
`sigma8`

Methods

__call__(r[, smoothing, kmin, kmax]) Return the correlation function (dimensionless) for separations r

__call__(r, smoothing=0.0, kmin=1e-05, kmax=10.0)[source]¶

Return the correlation function (dimensionless) for separations r

Parameters:

Parameters:	r (float, array_like) – the separation array in units of \(h^{-1} \mathrm(Mpc)\) smoothing (float, optional) – the std deviation of the Fourier space Gaussian smoothing to apply to P(k) before taking the FFT kmin (float, optional) – the minimum `k` value to compute P(k) for before taking the FFT kmax (float, optional) – the maximum `k` value to compute P(k) for before taking the FFT

r (float, array_like) – the separation array in units of \(h^{-1} \mathrm(Mpc)\)
smoothing (float, optional) – the std deviation of the Fourier space Gaussian smoothing to apply to P(k) before taking the FFT
kmin (float, optional) – the minimum k value to compute P(k) for before taking the FFT
kmax (float, optional) – the maximum k value to compute P(k) for before taking the FFT

nbodykit.cosmology.correlation.pk_to_xi(k, Pk, extrap=True)[source]¶

Return a callable function returning the correlation function, as computed from the Fourier transform of the input \(k\) and \(P(k)\) arrays.

This uses the mcfit package perform the FFT.

Parameters:	k (array_like) – wavenumbers where `Pk` is evaluated Pk (array_like) – the array holding the power spectrum values extrap (bool, optional) – whether to extrapolate the power spectrum with a power law; can improve the smoothness of the FFT
Returns:	a spline holding the interpolated correlation function values
Return type:	InterpolatedUnivariateSpline

nbodykit.cosmology.correlation.xi_to_pk(r, xi, extrap=False)[source]¶

Return a callable function returning the power spectrum, as computed from the Fourier transform of the input \(r\) and \(\xi(r)\) arrays.

This uses the mcfit package perform the FFT.

Parameters:	r (array_like) – separation values where `xi` is evaluated xi (array_like) – the array holding the correlation function values extrap (bool, optional) – whether to extrapolate the power spectrum with a power law; can improve the smoothness of the FFT
Returns:	a spline holding the interpolated power spectrum values
Return type:	InterpolatedUnivariateSpline