spotter.utils

Utility functions for spherical harmonics, HEALPix, and conversions.

This module provides helper functions for working with spherical harmonics, converting between representations, and mapping to HEALPix.

Functions

sigmoid(x[, scale])	Numerically stable sigmoid function.
y1d_to_2d(→ numpy.ndarray)	Convert 1D starry Ylm to 2D s2fft format.
y2d_to_1d(→ numpy.ndarray)	Convert 2D s2fft Ylm to 1D starry format.
C(l)	Complex to real spherical harmonics conversion matrix.
ylm_to_hp(y, N)	Convert a ylm array (starry-like) to healpy coefficients and map.

Module Contents

spotter.utils.sigmoid(x, scale=1000)

Numerically stable sigmoid function.

Parameters:

• x (float or array_like) – Input value(s).

• scale (float, optional) – Scaling factor (default 1000).

Returns:

y – Output value(s) in [0, 1].

Return type:

float or array_like

spotter.utils.y1d_to_2d(ydeg: int, flm_1d: numpy.ndarray) → numpy.ndarray

Convert 1D starry Ylm to 2D s2fft format.

Parameters:

• ydeg (int) – Maximum degree.

• flm_1d (ndarray) – 1D array of coefficients.

Returns:

flm_2d – 2D array of coefficients.

Return type:

ndarray

spotter.utils.y2d_to_1d(ydeg: int, flm_2d: numpy.ndarray) → numpy.ndarray

Convert 2D s2fft Ylm to 1D starry format.

Parameters:

• ydeg (int) – Maximum degree.

• flm_2d (ndarray) – 2D array of coefficients.

Returns:

flm_1d – 1D array of coefficients.

Return type:

ndarray

spotter.utils.C(l)

Complex to real spherical harmonics conversion matrix.

Parameters:

l (int) – Degree.

Returns:

C – Conversion matrix.

Return type:

ndarray

spotter.utils.ylm_to_hp(y, N)

Convert a ylm array (starry-like) to healpy coefficients and map.

Parameters:

• y (ndarray) – Spherical harmonic coefficients.

• N (int) – HEALPix nside.

Returns:

mh – HEALPix map.

Return type:

ndarray