From dd5e819c04a33e4e3e7c563cdd500b0cf89e0fbe Mon Sep 17 00:00:00 2001
From: Dan F-M <foreman.mackey@gmail.com>
Date: Thu, 19 Sep 2019 16:32:53 -0400
Subject: [PATCH] fixing normaliztion of vaneylen distribution

---
 exoplanet/distributions/eccentricity.py      |  2 +-
 exoplanet/distributions/eccentricity_test.py | 44 +++++++++++++++-----
 2 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/exoplanet/distributions/eccentricity.py b/exoplanet/distributions/eccentricity.py
index de79bb9d2..062c2f5cc 100644
--- a/exoplanet/distributions/eccentricity.py
+++ b/exoplanet/distributions/eccentricity.py
@@ -135,7 +135,7 @@ def vaneylen19(name, fixed=False, multi=False, model=None, **kwargs):
                     "frac", mu=frac_mu, sd=frac_sd, testval=frac_mu
                 )
 
-            gauss = pm.Normal.dist(mu=0, sd=sigma_gauss)
+            gauss = pm.HalfNormal.dist(sigma=sigma_gauss)
             rayleigh = pm.Weibull.dist(
                 alpha=2, beta=np.sqrt(2) * sigma_rayleigh
             )
diff --git a/exoplanet/distributions/eccentricity_test.py b/exoplanet/distributions/eccentricity_test.py
index 0dc35eb34..5c75ea90e 100644
--- a/exoplanet/distributions/eccentricity_test.py
+++ b/exoplanet/distributions/eccentricity_test.py
@@ -2,7 +2,7 @@
 
 import pytest
 import numpy as np
-from scipy.stats import kstest, beta
+from scipy.stats import kstest, beta, halfnorm, rayleigh
 
 from .base_test import _Base
 from .eccentricity import kipping13, vaneylen19
@@ -64,15 +64,7 @@ def test_kipping13_short(self):
         s, p = kstest(ecc, cdf)
         assert s < 0.05
 
-    @pytest.mark.parametrize(
-        "kwargs",
-        [
-            dict(),
-            dict(fixed=True),
-            dict(multi=True),
-            dict(fixed=True, multi=True),
-        ],
-    )
+    @pytest.mark.parametrize("kwargs", [dict(), dict(multi=True)])
     def test_vaneylen19(self, kwargs):
         with self._model() as model:
             dist = vaneylen19("ecc", shape=(5, 2), **kwargs)
@@ -91,3 +83,35 @@ def test_vaneylen19(self, kwargs):
 
         ecc = trace["ecc"]
         assert np.all((0 <= ecc) & (ecc <= 1))
+
+    def test_vaneylen19_single(self):
+        with self._model():
+            vaneylen19("ecc", fixed=True, multi=False, shape=2)
+            trace = self._sample()
+
+        ecc = trace["ecc"].flatten()
+        assert np.all((0 <= ecc) & (ecc <= 1))
+
+        f = 0.76
+        cdf = lambda x: (  # NOQA
+            (1 - f) * halfnorm.cdf(x, scale=0.049)
+            + f * rayleigh.cdf(x, scale=0.26)
+        )
+        s, p = kstest(ecc, cdf)
+        assert s < 0.05
+
+    def test_vaneylen19_multi(self):
+        with self._model():
+            vaneylen19("ecc", fixed=True, multi=True, shape=3)
+            trace = self._sample()
+
+        ecc = trace["ecc"].flatten()
+        assert np.all((0 <= ecc) & (ecc <= 1))
+
+        f = 0.08
+        cdf = lambda x: (  # NOQA
+            (1 - f) * halfnorm.cdf(x, scale=0.049)
+            + f * rayleigh.cdf(x, scale=0.26)
+        )
+        s, p = kstest(ecc, cdf)
+        assert s < 0.05