ENH: percentile function with additional parameters and vecorization

The percentile function was enhanced by adding limit and interpolation
parameters to give it similar functionality to SciPy's stats.scoreatpercentile
function.  In addition the function was vecorized along q and rewritten to
use the partition method for better performance.

1 files changed, 117 insertions, 20 deletions

diff --git a/numpy/lib/tests/test_function_base.py b/numpy/lib/tests/test_function_base.py
index f52eb5fbe..02597c78b 100644
--- a/numpy/lib/tests/test_function_base.py
+++ b/numpy/lib/tests/test_function_base.py
@@ -1440,27 +1440,124 @@ def compare_results(res, desired):
         assert_array_equal(res[i], desired[i])
 
 
-def test_percentile_list():
-    assert_equal(np.percentile([1, 2, 3], 0), 1)
+class TestScoreatpercentile(TestCase):
 
-
-def test_percentile_out():
-    x = np.array([1, 2, 3])
-    y = np.zeros((3,))
-    p = (1, 2, 3)
-    np.percentile(x, p, out=y)
-    assert_equal(y, np.percentile(x, p))
-
-    x = np.array([[1, 2, 3],
-                  [4, 5, 6]])
-
-    y = np.zeros((3, 3))
-    np.percentile(x, p, axis=0, out=y)
-    assert_equal(y, np.percentile(x, p, axis=0))
-
-    y = np.zeros((3, 2))
-    np.percentile(x, p, axis=1, out=y)
-    assert_equal(y, np.percentile(x, p, axis=1))
+    def test_basic(self):
+        x = np.arange(8) * 0.5
+        assert_equal(np.percentile(x, 0), 0.)
+        assert_equal(np.percentile(x, 100), 3.5)
+        assert_equal(np.percentile(x, 50), 1.75)
+
+    def test_2D(self):
+        x = np.array([[1, 1, 1],
+                     [1, 1, 1],
+                     [4, 4, 3],
+                     [1, 1, 1],
+                     [1, 1, 1]])
+        assert_array_equal(np.percentile(x, 50, axis=0), [[1, 1, 1]])
+
+    def test_limit(self):
+        x = np.arange(10)
+        assert_equal(np.percentile(x, 50, limit=(2, 5)), 3.5)
+        assert_equal(np.percentile([2, 3, 4, 5], 50), 3.5)
+
+        assert_equal(np.percentile(x, 50, limit=(-1, 8)), 4)
+        assert_equal(np.percentile([0, 1, 2, 3, 4, 5, 6, 7, 8], 50), 4)
+
+        assert_equal(np.percentile(x, 50, limit=(4, 11)), 6.5)
+        assert_equal(np.percentile([4, 5, 6, 7, 8, 9], 50, ), 6.5)
+
+    def test_linear(self):
+
+        # Test defaults
+        assert_equal(np.percentile(range(10), 50), 4.5)
+        assert_equal(np.percentile(range(10), 50, (2, 7)), 4.5)
+        assert_equal(np.percentile(range(100), 50, limit=(1, 8)), 4.5)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, (10, 100)), 55)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, (1, 10)), 5.5)
+
+        # explicitly specify interpolation_method 'fraction' (the default)
+        assert_equal(np.percentile(range(10), 50,
+                                   interpolation='linear'), 4.5)
+        assert_equal(np.percentile(range(10), 50, limit=(2, 7),
+                                   interpolation='linear'), 4.5)
+        assert_equal(np.percentile(range(100), 50, limit=(1, 8),
+                                   interpolation='linear'), 4.5)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, (10, 100),
+                                   interpolation='linear'), 55)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, (1, 10),
+                                   interpolation='linear'), 5.5)
+
+    def test_lower_higher(self):
+
+        # interpolation_method 'lower'/'higher'
+        assert_equal(np.percentile(range(10), 50,
+                                   interpolation='lower'), 4)
+        assert_equal(np.percentile(range(10), 50,
+                                   interpolation='higher'), 5)
+        assert_equal(np.percentile(range(10), 50, (2, 7),
+                                   interpolation='lower'), 4)
+        assert_equal(np.percentile(range(10), 50, limit=(2, 7),
+                                   interpolation='higher'), 5)
+        assert_equal(np.percentile(range(100), 50, (1, 8),
+                                   interpolation='lower'), 4)
+        assert_equal(np.percentile(range(100), 50, (1, 8),
+                                   interpolation='higher'), 5)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, (10, 100),
+                                   interpolation='lower'), 10)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, limit=(10, 100),
+                                   interpolation='higher'), 100)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, (1, 10),
+                                   interpolation='lower'), 1)
+        assert_equal(np.percentile(np.array([1, 10, 100]), 50, limit=(1, 10),
+                                   interpolation='higher'), 10)
+
+    def test_sequence(self):
+        x = np.arange(8) * 0.5
+        assert_equal(np.percentile(x, [0, 100, 50]), [0, 3.5, 1.75])
+
+    def test_axis(self):
+        x = np.arange(12).reshape(3, 4)
+
+        assert_equal(np.percentile(x, (25, 50, 100)), [2.75, 5.5, 11.0])
+
+        r0 = [[2, 3, 4, 5], [4, 5, 6, 7], [8, 9, 10, 11]]
+        assert_equal(np.percentile(x, (25, 50, 100), axis=0), r0)
+
+        r1 = [[0.75, 1.5, 3], [4.75, 5.5, 7], [8.75, 9.5, 11]]
+        assert_equal(np.percentile(x, (25, 50, 100), axis=1), r1)
+
+    def test_exception(self):
+        assert_raises(ValueError, np.percentile, [1, 2], 56,
+                      interpolation='foobar')
+        assert_raises(ValueError, np.percentile, [1], 101)
+        assert_raises(ValueError, np.percentile, [1], -1)
+
+    def test_percentile_list(self):
+        assert_equal(np.percentile([1, 2, 3], 0), 1)
+
+    def test_percentile_out(self):
+        x = np.array([1, 2, 3])
+        y = np.zeros((3,))
+        p = (1, 2, 3)
+        np.percentile(x, p, out=y)
+        assert_equal(y, np.percentile(x, p))
+
+        x = np.array([[1, 2, 3],
+                      [4, 5, 6]])
+
+        y = np.zeros((3, 3))
+        np.percentile(x, p, axis=0, out=y)
+        assert_equal(y, np.percentile(x, p, axis=0))
+
+        y = np.zeros((2, 3))
+        np.percentile(x, p, axis=1, out=y)
+        assert_equal(y, np.percentile(x, p, axis=1))
+
+    def test_percentile_no_overwrite(self):
+        a = np.array([2, 3, 4, 1])
+        np.percentile(a, [50], overwrite_input=False)
+        assert_equal(a, np.array([2, 3, 4, 1]))
 
 
 class TestMedian(TestCase):