"""Class MorphSqueeze -- Apply a polynomial to squeeze the morph
function."""
from numpy.polynomial import Polynomial
from scipy.interpolate import CubicSpline
from diffpy.morph.morphs.morph import LABEL_GR, LABEL_RA, Morph
[docs]
class MorphSqueeze(Morph):
"""Squeeze the morph function.
This applies a polynomial to squeeze the morph non-linearly.
Configuration Variables
-----------------------
squeeze : Dictionary
The polynomial coefficients {a0, a1, ..., an} for the squeeze
function where the polynomial would be of the form
a0 + a1*x + a2*x^2 and so on. The order of the polynomial is
determined by the length of the dictionary.
Returns
-------
A tuple (x_morph_out, y_morph_out, x_target_out, y_target_out)
where the target values remain the same and the morph data is
shifted according to the squeeze. The morphed data is returned on
the same grid as the unmorphed data.
Example
-------
Import the squeeze morph function:
>>> from diffpy.morph.morphs.morphsqueeze import MorphSqueeze
Provide initial guess for squeezing coefficients:
>>> squeeze_coeff = {"a0":0.1, "a1":-0.01, "a2":0.005}
Run the squeeze morph given input morph array (x_morph, y_morph) and target
array (x_target, y_target):
>>> morph = MorphSqueeze()
>>> morph.squeeze = squeeze_coeff
>>> x_morph_out, y_morph_out, x_target_out, y_target_out =
... morph(x_morph, y_morph, x_target, y_target)
To access parameters from the morph instance:
>>> x_morph_in = morph.x_morph_in
>>> y_morph_in = morph.y_morph_in
>>> x_target_in = morph.x_target_in
>>> y_target_in = morph.y_target_in
>>> squeeze_coeff_out = morph.squeeze
"""
# Define input output types
summary = "Squeeze morph by polynomial shift"
xinlabel = LABEL_RA
yinlabel = LABEL_GR
xoutlabel = LABEL_RA
youtlabel = LABEL_GR
parnames = ["squeeze"]
# extrap_index_low: last index before interpolation region
# extrap_index_high: first index after interpolation region
extrap_index_low = None
extrap_index_high = None
squeeze_cutoff_low = None
squeeze_cutoff_high = None
def __init__(self, config=None):
super().__init__(config)
[docs]
def morph(self, x_morph, y_morph, x_target, y_target):
"""Apply a polynomial to squeeze the morph function.
The morphed data is returned on the same grid as the unmorphed
data.
"""
Morph.morph(self, x_morph, y_morph, x_target, y_target)
coeffs = [self.squeeze[f"a{i}"] for i in range(len(self.squeeze))]
squeeze_polynomial = Polynomial(coeffs)
x_squeezed = self.x_morph_in + squeeze_polynomial(self.x_morph_in)
self.y_morph_out = CubicSpline(x_squeezed, self.y_morph_in)(
self.x_morph_in
)
self.set_extrapolation_info(x_squeezed, self.x_morph_in)
return self.xyallout