Handle changes in statsmodels behavior

In the latest stable release (0.14.0) statsmodels does not
yield an exception anymore when data is perfectly separable
this restores the expected behavior, though this may become
a problem in future versions

pyseer/model.py

@@ -107,6 +107,12 @@ def fit_null(p, m, cov, continuous, firth=False):
         start_vec[0] = np.log(np.mean(p)/(1-np.mean(p)))
         null_mod = smf.Logit(p, v)
 
+    # statsmodels does not raise exceptions with perfectly separable data
+    # but just a warning
+    # this may stop working in the future
+    # source: https://github.com/statsmodels/statsmodels/blob/e12de82fabd8e3fd71413aae384763c1442c4516/statsmodels/discrete/discrete_model.py#L186
+    null_mod.raise_on_perfect_prediction = True
+
     try:
         if continuous:
             null_res = null_mod.fit(disp=False)
@@ -173,6 +179,11 @@ def fit_lineage_effect(lin, c, k):
                            axis=1)
 
     lineage_mod = smf.Logit(k, X)
+    # statsmodels does not raise exceptions with perfectly separable data
+    # but just a warning
+    # this may stop working in the future
+    # source: https://github.com/statsmodels/statsmodels/blob/e12de82fabd8e3fd71413aae384763c1442c4516/statsmodels/discrete/discrete_model.py#L186
+    lineage_mod.raise_on_perfect_prediction = True
     try:
         lineage_res = lineage_mod.fit(method='newton', disp=False)
 
@@ -287,6 +298,11 @@ def fixed_effects_regression(variant, p, k, m, c, af, pattern,
     try:
         if continuous:
             mod = smf.OLS(p, v)
+            # statsmodels does not raise exceptions with perfectly separable data
+            # but just a warning
+            # this may stop working in the future
+            # source: https://github.com/statsmodels/statsmodels/blob/e12de82fabd8e3fd71413aae384763c1442c4516/statsmodels/discrete/discrete_model.py#L186
+            mod.raise_on_perfect_prediction = True
 
             res = mod.fit()
             intercept = res.params[0]
@@ -298,6 +314,11 @@ def fixed_effects_regression(variant, p, k, m, c, af, pattern,
 
         else:
             mod = smf.Logit(p, v)
+            # statsmodels does not raise exceptions with perfectly separable data
+            # but just a warning
+            # this may stop working in the future
+            # source: https://github.com/statsmodels/statsmodels/blob/e12de82fabd8e3fd71413aae384763c1442c4516/statsmodels/discrete/discrete_model.py#L186
+            mod.raise_on_perfect_prediction = True
 
             start_vec = np.zeros(v.shape[1])
             start_vec[0] = np.log(np.mean(p)/(1-np.mean(p)))

tests/model_test.py

@@ -9,6 +9,7 @@
 try:
     smf.Logit
 except AttributeError:
+    import statsmodels
     smf.Logit = statsmodels.discrete.discrete_model.Logit
 from pyseer.model import pre_filtering
 from pyseer.model import fit_null