Fixed bug in treatment of noisy_percentile=-1 edge case. Resolves #939.…

… Agreed, @mclaughlin6464?
astropy · Jan 7, 2020 · 33946dd · 33946dd
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commit 33946dd
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diff --git a/halotools/empirical_models/abunmatch/noisy_percentile.py b/halotools/empirical_models/abunmatch/noisy_percentile.py
@@ -147,8 +147,10 @@ def noisy_percentile(percentile, correlation_coeff, seed=None, random_percentile
     Correlation strengths between zero and unity span the intermediary cases.
 
     """
-    if np.all(np.abs(correlation_coeff) == 1):
+    if np.all(correlation_coeff == 1):
         return percentile
+    elif np.all(correlation_coeff == -1):
+        return percentile[::-1]
 
     percentile = np.atleast_1d(percentile)
     correlation_coeff = np.atleast_1d(correlation_coeff)

diff --git a/halotools/empirical_models/abunmatch/tests/test_noisy_percentile.py b/halotools/empirical_models/abunmatch/tests/test_noisy_percentile.py
@@ -39,3 +39,11 @@ def test_noisy_percentile3():
     u2 = noisy_percentile(u, r_desired, random_percentile=uran)
     r_achieved = spearmanr(u, u2)[0]
     assert np.allclose(r_desired, r_achieved, atol=0.02)
+
+
+def test_negative_unity_noisy_percentile():
+    """Regression test for #939.
+    """
+    r_desired = -1
+    u2 = noisy_percentile(u, r_desired, seed=fixed_seed)
+    assert np.allclose(u2, u[::-1])