[SPARK-6576] [MLlib] [PySpark] DenseMatrix in PySpark should support indexing

Support indexing in DenseMatrices in PySpark

Author: MechCoder <manojkumarsivaraj334@gmail.com>

Closes #5232 from MechCoder/SPARK-6576 and squashes the following commits:

a735078 [MechCoder] Change bounds
a062025 [MechCoder] Matrices are stored in column order
7917bc1 [MechCoder] [SPARK-6576] DenseMatrix in PySpark should support indexing

python/pyspark/mllib/linalg.py

@@ -670,6 +670,16 @@ class DenseMatrix(Matrix):
         """
         return self.values.reshape((self.numRows, self.numCols), order='F')
 
+    def __getitem__(self, indices):
+        i, j = indices
+        if i < 0 or i >= self.numRows:
+            raise ValueError("Row index %d is out of range [0, %d)"
+                             % (i, self.numRows))
+        if j >= self.numCols or j < 0:
+            raise ValueError("Column index %d is out of range [0, %d)"
+                             % (j, self.numCols))
+        return self.values[i + j * self.numRows]
+
     def __eq__(self, other):
         return (isinstance(other, DenseMatrix) and
                 self.numRows == other.numRows and

python/pyspark/mllib/tests.py

@@ -135,6 +135,13 @@ class VectorTests(PySparkTestCase):
         for ind in [4, -5, 7.8]:
             self.assertRaises(ValueError, sv.__getitem__, ind)
 
+    def test_matrix_indexing(self):
+        mat = DenseMatrix(3, 2, [0, 1, 4, 6, 8, 10])
+        expected = [[0, 6], [1, 8], [4, 10]]
+        for i in range(3):
+            for j in range(2):
+                self.assertEquals(mat[i, j], expected[i][j])
+
 
 class ListTests(PySparkTestCase):