determine_ellipse#

pyxem.utils.ransac_ellipse_tools.determine_ellipse(signal=None, pos=None, mask=None, num_points=1000, use_ransac=False, guess_starting_params=True, return_params=False, **kwargs)[source]#

This method starts by taking some number of points which are the most intense in the signal or those points can be directly passed. It then takes those points and guesses some starting parameters for the get_ellipse_model_ransac_single_frame function. From there it will try to determine the ellipse parameters.

Parameters:

signal (Signal2D) – The signal of interest.
pos (np.ndarray) – The positions of the points to be used to determine the ellipse.
mask (Array-like) – The mask to be applied to the data. The True values are ignored.
num_points (int) – The number of points to consider.
use_ransac (bool) – If Ransac should be used to determine the ellipse. False is faster but less. robust with respect to noise.
guess_starting_params (bool) – If True then the starting parameters will be guessed based on the points determined.
return_params (bool) – If the ellipse parameters should be returned as well.
**kwargs – Any other keywords for get_ellipse_model_ransac_single_frame.

Returns:

center ((x,y)) – The center of the diffraction pattern.
affine – The affine transformation to make the diffraction pattern circular.

Examples

>>> import pyxem.utils.ransac_ellipse_tools as ret
>>> import pyxem.data.dummy_data.make_diffraction_test_data as mdtd
>>> test_data = mdtd.MakeTestData(200, 200, default=False)
>>> test_data.add_disk(x0=100, y0=100, r=5, intensity=30)
>>> test_data.add_ring_ellipse(x0=100, y0=100, semi_len0=63, semi_len1=70, rotation=45)
>>> s = test_data.signal
>>> s.set_signal_type("electron_diffraction")
>>> import numpy as np
>>> mask = np.zeros_like(s.data, dtype=bool)
>>> mask[100 - 20:100 + 20, 100 - 20:100 + 20] = True # mask beamstop
>>> center, affine = ret.determine_ellipse(s, mask=mask, use_ransac=False)
>>> s_corr = s.apply_affine_transformation(affine, inplace=False)