Broke crop_by_extra_coord API to be similar to crop_by_coords.

CHANGELOG.rst

@@ -1,6 +1,16 @@
 1.1 (Unreleased)
 ================
 
+API-Breaking Changes
+--------------------
+- `~ndcube.NDCubeBase.crop_by_extra_coord` API has been broken and
+  replaced.
+  Old version:
+  ``crop_by_extra_coord(min_coord_value, interval_width, coord_name)``.
+  New version:
+  ``crop_by_extra_coord(coord_name, min_coord_value,  max_coord_value)``.
+  [#142]
+
 New Features
 ------------
 - Created a new `~ndcube.NDCubeBase` which has all the functionality

ndcube/ndcube.py

@@ -481,36 +481,38 @@ def crop_by_coords(self, lower_corner, interval_widths=None, upper_corner=None,
                       for axis_pixels in all_pix_corners])
         return self[item]
 
-    def crop_by_extra_coord(self, min_coord_value, interval_width, coord_name):
+    def crop_by_extra_coord(self, coord_name, min_coord_value, max_coord_value):
         """
         Crops an NDCube given a minimum value and interval width along an extra coord.
 
         Parameters
         ----------
+        coord_name: `str`
+            Name of extra coordinate by which to crop.
+
         min_coord_value: Single value `astropy.units.Quantity`
             The minimum desired value of the extra coord after cropping.
             Unit must be consistent with the extra coord on which cropping is based.
 
-        interval_width: Single value `astropy.units.Quantity`
-            The width of the interval along the extra coord axis in physical units
-            consistent with the extra coord.  Unit must be consistent with the extra
-            coord on which cropping is based.
-
-        extra_coord: `str`
-            Name of extra coordinate.
+        min_coord_value: Single value `astropy.units.Quantity`
+            The maximum desired value of the extra coord after cropping.
+            Unit must be consistent with the extra coord on which cropping is based.
 
         Returns
         -------
         result: `ndcube.NDCube`
 
         """
+        if not isinstance(coord_name, str):
+            raise TypeError("The API for this function has changed. "
+                            "Please give coord_name, min_coord_value, max_coord_value")
         extra_coord_dict = self.extra_coords[coord_name]
         if isinstance(extra_coord_dict["value"], u.Quantity):
             extra_coord_values = extra_coord_dict["value"]
         else:
             extra_coord_values = np.asarray(extra_coord_dict["value"])
         w = np.logical_and(extra_coord_values >= min_coord_value,
-                           extra_coord_values < min_coord_value + interval_width)
+                           extra_coord_values < max_coord_value)
         w = np.arange(len(extra_coord_values))[w]
         item = [slice(None)]*len(self.dimensions)
         item[extra_coord_dict["axis"]] = slice(w[0], w[1]+1)

ndcube/tests/test_ndcube.py

@@ -865,9 +865,9 @@ def test_crop_by_coords_error(test_input):
 
 @pytest.mark.parametrize(
     "test_input,expected",
-    [((cubem, 0*u.pix, 1.5*u.pix, "time"), cubem[0:2]),
-     ((cube, 0*u.pix, 1.5*u.pix, "bye"), cube[:, :, 0:2]),
-     ((cubet, datetime.datetime(2000, 1, 1), datetime.timedelta(minutes=2), "time"), cubet[:2])])
+    [((cubem, "time", 0*u.pix, 1.5*u.pix, ), cubem[0:2]),
+     ((cube, "bye", 0*u.pix, 1.5*u.pix, ), cube[:, :, 0:2]),
+     ((cubet, "time", datetime.datetime(2000, 1, 1), datetime.datetime(2000, 1, 3)), cubet[:2])])
 def test_crop_by_extra_coord(test_input, expected):
     helpers.assert_cubes_equal(
         test_input[0].crop_by_extra_coord(*tuple(test_input[1:])), expected)