resolves #210

chainladder/__init__.py

@@ -43,4 +43,4 @@ def auto_sparse(auto_sparse=True):
 from chainladder.methods import *  # noqa (API Import)
 from chainladder.workflow import *  # noqa (API Import)
 
-__version__ = "0.8.8"
+__version__ = "0.8.9"

chainladder/core/base.py

@@ -215,13 +215,19 @@ def _to_datetime(data, fields, period_end=False, format=None):
     def _development_lag(origin, development):
         """ For tabular format, this will convert the origin/development
             difference to a development lag """
-        return ((development - origin) / 
+        return ((development - origin) /
                 np.timedelta64(1, 'M')).round(0).astype(int)
-    
+
     @staticmethod
     def _get_grain(array):
-        return {1: "Y", 2: "S", 4: "Q"}.get(
-            len(set(pd.Series(array.unique()).dt.month)), "M")
+        u = pd.Series(array).dt.month.sort_values().diff().dropna().unique()
+        u = u[u>0]
+        if len(u) > 1:
+            return 'M'
+        elif len(u) == 0:
+            return 'Y'
+        else:
+            return {6: "2Q", 3: "Q"}.get(u[0], "M")
 
     @staticmethod
     def _cartesian_product(*arrays):

chainladder/core/pandas.py

@@ -380,6 +380,7 @@ def aggregate(i, obj, axis, v):
             odims = self.obj._to_datetime(
                 pd.Series(self.groups.indices.keys()).to_frame(), [0])
             obj.origin_grain = self.obj._get_grain(odims)
+            obj.origin_grain = 'S' if obj.origin_grain == '2Q' else obj.origin_grain
             obj.odims = odims.values
         obj._set_slicers()
         if auto_sparse:

chainladder/core/tests/test_triangle.py

@@ -356,3 +356,12 @@ def test_inplace(raa):
     t.dev_to_val(inplace=True)
     t.val_to_dev(inplace=True)
     t.grain('OYDY', inplace=True)
+
+def test_malformed_init():
+    assert cl.Triangle(
+        data=pd.DataFrame({
+            'Accident Date': ['2020-07-23', '2019-07-23', '2018-07-23', '2016-07-23', '2020-08-23', '2019-09-23', '2018-10-23'],
+            'Valuation Date': ['2021-01-01', '2021-01-01', '2021-01-01', '2021-01-01', '2021-01-01', '2021-01-01', '2021-01-01'],
+            'Loss': [10000, 10000, 10000, 10000, 0, 0, 0]}),
+        origin='Accident Date', development='Valuation Date', columns='Loss'
+    ).origin_grain == 'M'

chainladder/core/triangle.py

@@ -116,6 +116,7 @@ def __init__(self, data=None, origin=None, development=None, columns=None,
         origin_date = self._to_datetime(
             data, origin, format=origin_format).rename('__origin__')
         self.origin_grain = self._get_grain(origin_date)
+        self.origin_grain = 'S' if self.origin_grain == '2Q' else self.origin_grain
         development_date = self._set_development(
             data, development, development_format, origin_date)
         self.development_grain = (

setup.py

@@ -14,7 +14,7 @@
 descr = "Chainladder Package - P&C Loss Reserving package "
 name = 'chainladder'
 url = '/~https://github.com/casact/chainladder-python'
-version='0.8.8' # Put this in __init__.py
+version='0.8.9' # Put this in __init__.py
 
 data_path = ''
 setup(