ENH : First attempt to add sparse_pivot

pandas/core/reshape.py

@@ -336,6 +336,19 @@ def pivot(self, index=None, columns=None, values=None):
         return indexed.unstack(columns)
 
 
+def pivot_sparse(index, columns, values):
+    if (len(index) != len(columns)) or (len(columns) != len(values)):
+        raise AssertionError('Length of index, columns, and values must be the'
+                             ' same')
+
+    if len(index) == 0:
+        return SparseSeries(index=[])
+
+    hindex = MultiIndex.from_arrays([index, columns])
+    series = Series(values.values, index=hindex)
+    return series.to_sparse()
+
+
 def pivot_simple(index, columns, values):
     """
     Produce 'pivot' table based on 3 columns of this DataFrame.

pandas/tests/test_reshape.py

@@ -11,7 +11,7 @@
 
 from pandas.util.testing import assert_frame_equal
 
-from pandas.core.reshape import (melt, lreshape, get_dummies, wide_to_long)
+from pandas.core.reshape import (melt, lreshape, get_dummies, wide_to_long, pivot_sparse)
 import pandas.util.testing as tm
 from pandas.compat import range, u
 
@@ -717,6 +717,19 @@ def test_stubs(self):
         self.assertEqual(stubs, ['inc', 'edu'])
 
 
+class TestSparePivot(tm.TestCase):
+
+    def setUp(self):
+        self.df = pd.DataFrame({'a': ['a', 'b', 'b', 'c'],\
+                                'b': ['x', 'x', 'y', 'z'],\
+                                'c': [1, 2, 3, 4]})
+
+    def test_simile_sparse_pivot(self):
+        result = pivot_sparse(self.df['a'], self.df['b'], self.df['c'])
+        actual_get = np.asarray(result.to_coo()[0].todense())
+        expected = self.df.pivot(index='a', columns='b', values='c').fillna(0).values.astype(self.df['c'].dtype)
+        self.assert_numpy_array_equal(actual_get, expected)
+
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],
                    exit=False)