class method for mct creation from dataframe

UDST · Apr 13, 2020 · c625072 · c625072
1 parent dbf56aa
commit c625072
Showing 1 changed file with 15 additions and 3 deletions.
diff --git a/choicemodels/tools/mergedchoicetable.py b/choicemodels/tools/mergedchoicetable.py
@@ -186,22 +186,34 @@ def __init__(self, observations, alternatives, chosen_alternatives=None,
     @classmethod
     def from_df(cls, df):
         """
-        Create an object instance from a dataframe
+        Create an object instance from a dataframe.
+
+        The MergedChoiceTable class requires two dataframes to initialize
+        representing observations and alternatives for the choice scenario,
+        so this classmethod simply passes in two empty dataframes. Similarly,
+        it also passes a dummy for the `chosen_alternatives` arg in order
+        to trigger the creation of the `MergedChoiceTable.choice_col` property.
 
         Parameters
         ----------
         df : a Pandas DataFrame object with 1) a MultiIndex in which the
         first level corresponds to the index of the observations and the
         second to the index of the alternatives; and 2) a binary column
-        named 'chosen' that indicated whether the corresponding 
+        named 'chosen' that indicated whether the corresponding
         alternative was chosen in the observation data.
+
+        choice_col : Name of the column containing a binary representation
+        of whether each alternative was chosen in the given choice scenario.
         
         Returns
         -------
         MergedChoiceTable
 
         """
-        obj = cls(pd.DataFrame(), pd.DataFrame())
+        obj = cls(
+            observations=pd.DataFrame(),
+            alternatives=pd.DataFrame(),
+            chosen_alternatives=-999)
         obj._merged_table = df
 
         return obj