add is_uniform_spaced function to utils

xray/core/utils.py

@@ -392,7 +392,17 @@ def close_on_error(f):
 def is_remote_uri(path):
     return bool(re.search('^https?\://', path))
 
-def is_uniform_spaced(arr):
-    """Return True if values of an array are uniformly spaced and sorted
+
+def is_uniform_spaced(arr, **kwargs):
+    """Return True if values of an array are uniformly spaced and sorted.
+
+    >>> is_uniform_spaced(range(5))
+    True
+    >>> is_uniform_spaced([-4, 0, 100])
+    False
+
+    kwargs are additional arguments to ``np.isclose``
     """
-    pass
+    arr = np.array(arr)
+    diffs = np.diff(arr)
+    return np.isclose(diffs.min(), diffs.max(), **kwargs)

xray/test/test_utils.py

@@ -121,8 +121,20 @@ def test_chain_map(self):
 
 class Test_is_uniform_and_sorted(TestCase):
 
-    def test_range_sorted(self):
+    def test_sorted_uniform(self):
         self.assertTrue(utils.is_uniform_spaced(np.arange(5)))
 
-    def test_not_sorted(self):
-        self.assertFalse(utils.is_uniform_spaced([4, 1, 89]))
+    def test_sorted_not_uniform(self):
+        self.assertEqual(False, utils.is_uniform_spaced([-2, 1, 89]))
+
+    def test_not_sorted_uniform(self):
+        self.assertEqual(False, utils.is_uniform_spaced([1, -1, 3]))
+
+    def test_not_sorted_not_uniform(self):
+        self.assertEqual(False, utils.is_uniform_spaced([4, 1, 89]))
+
+    def test_two_numbers(self):
+        self.assertTrue(utils.is_uniform_spaced([0, 1.7]))
+
+    def test_relative_tolerance(self):
+        self.assertTrue(utils.is_uniform_spaced([0, 0.97, 2], rtol=0.1))