Source code for islatu.corrections

Reflectometry data must be corrected as a part of reduction.
These functions facilitate this, including the footprint and
DCD q-variance corrections.

import numpy as np
from scipy.stats import norm
from scipy.interpolate import splrep

[docs]def footprint_correction(beam_width, sample_size, theta): """ The factor by which the intensity should be multiplied to account for the scattering geometry, where the beam is Gaussian in shape. Args: beam_width (:py:attr:`float`): Width of incident beam, in metres. sample_size (:py:attr:`float`): Width of sample in the dimension of the beam, in metres. theta (:py:attr:`float`): Incident angle, in degrees. Returns: Array of correction factors. """ # Deal with the [trivial] theta=0 case. theta = np.array([10**(-3) if t == 0 else t for t in theta]) beam_sd = beam_width / 2 / np.sqrt(2 * np.log(2)) projected_beam_sd = beam_sd / np.sin(np.radians(theta)) frac_of_beam_sampled = ( norm.cdf(sample_size/2, 0, projected_beam_sd) - norm.cdf(-sample_size/2, 0, projected_beam_sd) ) return frac_of_beam_sampled
[docs]def get_interpolator( file_path, parser, q_axis_name="qdcd_", intensity_axis_name="adc2"): """ Get an interpolator object from scipy, this is useful for the DCD q-normalisation step. Args: file_path (:py:attr:`str`): File path to the normalisation file. parser (:py:attr:`callable`): Parser function for the normalisation file. q_axis_name (:py:attr:`str`, optional): Label for the q-value in the normalisation file. Defaults to ``'qdcd_'``. intensity_axis_name (:py:attr:`str`, optional): Label for the intensity in the normalisation file. Defaults to ``'adc2'``. Returns: :py:attr:`tuple`: Containing: - :py:attr:`array_like`: Interpolation knots. - :py:attr:`array_like`: B-spline coefficients. - :py:attr:`int`: Degree of spline. """ normalisation_data = parser(file_path)[1] return splrep( normalisation_data[q_axis_name], normalisation_data[intensity_axis_name])