Forward

This module provides the base class ForwardOperator. This operator combines transformation and measurement operators for forward modelling and calculation of the gradient of data fidelity for a given MCMC sample. This is the block of the MCMC algorithms that holds all the data. A couple of simple operators are also given that can be used out of the box.

class forward.ForwardOperator(data, sig_d, setting, transform=None, measurement=None, nparams=None)

Base Forward operator. Combines a transform and a measurement operator.

Parameters

  • data – observed data vector

  • sig_d – observed data error. Can be a single float, vector or covariance matrix.

  • setting (string) – analysis or synthesis

  • transform – type transforms.Transform to transform between bases

  • measurement – type measurements.Measurement to predict observed data

  • nparams (int) – number of sampled parameters/dimensions. Depends on parameterisation and setting.

forward(X)

Forward modelling, with or without basis transformation depending on setting.

Parameters

X – MCMC sample

Returns

data predictions

calc_gradg(preds)

Calculates gradient of data fidelity. Assumes Gaussian data errors

Parameters

preds – data predictions of current MCMC sample

Returns

gradient of Gaussian data fidelity

class forward.SphericalWaveletTransformOperator(data, sig_d, setting, L, B, J_min, dirs=1, spin=0)

Forward operator with a spherical wavelet transform and identity operator.

Parameters

  • L (int) – angular bandlimit

  • B (float) – wavelet scale parameter

  • J_min (int) – minimum wavelet scale

  • dirs (int) – azimuthal bandlimit for directional wavelets

  • spin (int) – spin number of spherical signal

class forward.PathIntegralOperator(pathmatrix, data, sig_d, setting, L, B, J_min, dirs=1, spin=0)

Forward operator with a spherical wavelet transform and a path integral measurement operator.

Todo

Since the measurement operator is just a matrix multiplication, can be renamed to something more generic.

Parameters

  • pathmatrix (array) – matrix describing a set of paths on the sphere

  • L (int) – angular bandlimit

  • B (float) – wavelet scale parameter

  • J_min (int) – minimum wavelet scale

  • dirs (int) – azimuthal bandlimit for directional wavelets

  • spin (int) – spin number of spherical signal