Function

NumCosmoMathsf_sbessel_xjl_deriv_from_array

Declaration [src]

gdouble
ncm_sf_sbessel_xjl_deriv_from_array (
  guint ell,
  gdouble x,
  const gdouble* jl_x
)

Description [src]

Computes $\left(x\, j_\ell(x)\right)’$ from precomputed $j_l(x)$ values using $\left(x\, j_\ell(x)\right)’ = x\, j_{\ell-1}(x) - \ell\, j_\ell(x)$. For $\ell = 0$ it returns $\cos(x)$ exactly.

This function is not directly available to language bindings.

Parameters

ell

Type: guint

Order $\ell$.

x

Type: gdouble

Argument $x$.

jl_x

Type: const gdouble*

$j_l(x)$ for $l = 0, \dots, \ell$ at least.

The data is owned by the caller of the function.

Return value

Type: gdouble

The value $\left(x\, j_\ell(x)\right)’$.