Squeeze morph: Adding UCs tests

news/morphsqueeze.rst

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+**Added:**
+
+* Polynomial squeeze of x-axis of morphed data
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

src/diffpy/morph/morphs/morphsqueeze.py

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+from diffpy.morph.morphs.morph import LABEL_GR, LABEL_RA, Morph
+
+
+class MorphSqueeze(Morph):
+    """Squeeze the morph function.
+
+    This applies a polynomial to squeeze the morph non-linearly. The morphed
+    data is returned on the same grid as the unmorphed data.
+
+    Configuration Variables
+    -----------------------
+    squeeze : list
+        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
+        list.
+
+    Example
+    -------
+    >>> import numpy as np
+    >>> from numpy.polynomial import Polynomial
+    >>> from diffpy.morph.morphs.morphsqueeze import MorphSqueeze
+
+    >>> x_target = np.linspace(0, 10, 101)
+    >>> y_target = np.sin(x_target)
+    >>> x_morph = np.linspace(0, 10, 101)
+    >>> squeeze_coeff = [0.1, -0.01, 0.005]
+    >>> poly = Polynomial(squeeze_coeff)
+    >>> y_morph = np.sin(x_morph + poly(x_morph))
+
+    >>> 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)
+    """
+
+    # Define input output types
+    summary = "Squeeze morph by polynomial shift"
+    xinlabel = LABEL_RA
+    yinlabel = LABEL_GR
+    xoutlabel = LABEL_RA
+    youtlabel = LABEL_GR
+    parnames = ["squeeze"]
+
+    def morph(self, x_morph, y_morph, x_target, y_target):
+        """Apply a polynomial to squeeze the morph function"""
+        Morph.morph(self, x_morph, y_morph, x_target, y_target)
+
+        return self.xyallout

tests/test_morphsqueeze.py

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+import numpy as np
+import pytest
+from numpy.polynomial import Polynomial
+
+from diffpy.morph.morphs.morphsqueeze import MorphSqueeze
+
+squeeze_coeffs_list = [
+    # The order of coefficients is [a0, a1, a2, ..., an]
+    # Negative cubic squeeze coefficients
+    [-0.2, -0.01, -0.001, -0.001],
+    # Positive cubic squeeze coefficients
+    [0.2, 0.01, 0.001, 0.001],
+    # Positive and negative cubic squeeze coefficients
+    [0.2, -0.01, 0.002, -0.001],
+    # Quadratic squeeze coefficients
+    [-0.2, 0.005, -0.007],
+    # Linear squeeze coefficients
+    [0.1, 0.3],
+    # 4th order squeeze coefficients
+    [0.2, -0.01, 0.001, -0.001, 0.0004],
+    # Zeros and non-zeros, the full polynomial is applied
+    [0, 0.03, 0, -0.001],
+    # Testing zeros, expect no squeezing
+    [0, 0, 0, 0, 0, 0],
+]
+morph_target_grids = [
+    # UCs from issue 181: https://github.com/diffpy/diffpy.morph/issues/181
+    # UC2: Same range and same grid density
+    (np.linspace(0, 10, 101), np.linspace(0, 10, 101)),
+    # UC4: Target range wider than morph, same grid density
+    (np.linspace(0, 10, 101), np.linspace(-2, 20, 221)),
+    # UC6: Target range wider than morph, target grid density finer than morph
+    (np.linspace(0, 10, 101), np.linspace(-2, 20, 421)),
+    # UC8: Target range wider than morph, morph grid density finer than target
+    (np.linspace(0, 10, 401), np.linspace(-2, 20, 200)),
+    # UC10: Morph range starts and ends earlier than target, same grid density
+    (np.linspace(-2, 10, 121), np.linspace(0, 20, 201)),
+    # UC12: Morph range wider than target, same grid density
+    (np.linspace(-2, 20, 221), np.linspace(0, 10, 101)),
+]
+
+
+@pytest.mark.parametrize("x_morph, x_target", morph_target_grids)
+@pytest.mark.parametrize("squeeze_coeffs", squeeze_coeffs_list)
+def test_morphsqueeze(x_morph, x_target, squeeze_coeffs):
+    y_target = np.sin(x_target)
+    squeeze_polynomial = Polynomial(squeeze_coeffs)
+    x_squeezed = x_morph + squeeze_polynomial(x_morph)
+    y_morph = np.sin(x_squeezed)
+    x_morph_expected = x_morph
+    y_morph_expected = np.sin(x_morph)
+    morph = MorphSqueeze()
+    morph.squeeze = squeeze_coeffs
+    x_morph_actual, y_morph_actual, x_target_actual, y_target_actual = morph(
+        x_morph, y_morph, x_target, y_target
+    )
+    assert np.allclose(y_morph_actual, y_morph_expected)
+    assert np.allclose(x_morph_actual, x_morph_expected)
+    assert np.allclose(x_target_actual, x_target)
+    assert np.allclose(y_target_actual, y_target)