Basic support for varying longitude ranges.

lib/iris/analysis/interpolate.py

@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2010 - 2012, Met Office
+# (C) British Crown Copyright 2010 - 2013, Met Office
 #
 # This file is part of Iris.
 #
@@ -645,6 +645,7 @@ def linear(cube, sample_points, extrapolation_mode='linear'):
         # Now we must be down to a single sample coordinate and its
         # values.
         src_coord, requested_points = sample_points[0]
+        sample_values = np.array(requested_points)
 
         # 1) Define the interpolation characteristics.
 
@@ -682,7 +683,12 @@ def linear(cube, sample_points, extrapolation_mode='linear'):
                                      cube.data.mask[tuple(coord_slice_in_cube)],
                                      axis=sample_dim)
                 data = ma.array(new_data, mask=new_mask)
-
+
+            # Map all the requested values into the range of the source
+            # data.
+            if modulus:
+                offset = src_coord.points[0]
+                sample_values = ((sample_values - offset) % modulus) + offset
         else:
             src_points = src_coord.points
             data = cube.data
@@ -721,7 +727,7 @@ def interpolate(fx, new_x, **kwargs):
             return new_fx
 
         # 2) Interpolate the data and produce our new Cube.
-        data = interpolate(data, requested_points, axis=sample_dim, copy=False)
+        data = interpolate(data, sample_values, axis=sample_dim, copy=False)
         new_cube = iris.cube.Cube(data)
         new_cube.metadata = cube.metadata
 

lib/iris/tests/analysis/__init__.py

@@ -0,0 +1,20 @@
+# (C) British Crown Copyright 2013, Met Office
+#
+# This file is part of Iris.
+#
+# Iris is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Iris is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with Iris.  If not, see <http://www.gnu.org/licenses/>.
+"""
+Package for testing the iris.analysis package.
+
+"""

lib/iris/tests/analysis/test_interpolate.py

@@ -0,0 +1,62 @@
+# (C) British Crown Copyright 2013, Met Office
+#
+# This file is part of Iris.
+#
+# Iris is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Iris is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with Iris.  If not, see <http://www.gnu.org/licenses/>.
+"""
+Test the iris.analysis.interpolate module.
+
+"""
+# Import iris tests first so that some things can be initialised before
+# importing anything else.
+import iris.tests as tests
+
+import numpy as np
+
+import iris.analysis.interpolate as interpolate
+from iris.coords import DimCoord
+from iris.cube import Cube
+
+
+class Test_linear__circular_wrapping(tests.IrisTest):
+    def _create_cube(self, longitudes):
+        # Return a Cube with circular longitude with the given values.
+        data = np.arange(12).reshape((3, 4)) * 0.1
+        cube = Cube(data)
+        lon = DimCoord(longitudes, standard_name='longitude',
+                       units='degrees', circular=True)
+        cube.add_dim_coord(lon, 1)
+        return cube
+
+    def test_symmetric(self):
+        # Check we can interpolate from a Cube defined over [-180, 180).
+        cube = self._create_cube([-180, -90, 0, 90])
+        samples = [('longitude', range(-360, 720, 45))]
+        result = interpolate.linear(cube, samples)
+        self.assertCMLApproxData(result, ('analysis', 'interpolation',
+                                          'linear', 'circular_wrapping',
+                                          'symmetric'))
+
+    def test_positive(self):
+        # Check we can interpolate from a Cube defined over [0, 360).
+        cube = self._create_cube([0, 90, 180, 270])
+        samples = [('longitude', range(-360, 720, 45))]
+        result = interpolate.linear(cube, samples)
+        self.assertCMLApproxData(result, ('analysis', 'interpolation',
+                                          'linear', 'circular_wrapping',
+                                          'positive'))
+
+
+if __name__ == "__main__":
+    tests.main()

lib/iris/tests/results/analysis/interpolation/linear/circular_wrapping/positive

@@ -0,0 +1,15 @@
+<?xml version="1.0" ?>
+<cubes xmlns="urn:x-iris:cubeml-0.2">
+  <cube units="unknown">
+    <coords>
+      <coord datadims="[1]">
+        <dimCoord id="a523d045" points="[-360.0, -315.0, -270.0, -225.0, -180.0, -135.0,
+		-90.0, -45.0, 0.0, 45.0, 90.0, 135.0, 180.0,
+		225.0, 270.0, 315.0, 360.0, 405.0, 450.0, 495.0,
+		540.0, 585.0, 630.0, 675.0]" shape="(24,)" standard_name="longitude" units="Unit('degrees')" value_type="float64"/>
+      </coord>
+    </coords>
+    <cellMethods/>
+    <data dtype="float64" shape="(3, 24)" state="loaded"/>
+  </cube>
+</cubes>

lib/iris/tests/results/analysis/interpolation/linear/circular_wrapping/symmetric

@@ -0,0 +1,15 @@
+<?xml version="1.0" ?>
+<cubes xmlns="urn:x-iris:cubeml-0.2">
+  <cube units="unknown">
+    <coords>
+      <coord datadims="[1]">
+        <dimCoord id="a523d045" points="[-360.0, -315.0, -270.0, -225.0, -180.0, -135.0,
+		-90.0, -45.0, 0.0, 45.0, 90.0, 135.0, 180.0,
+		225.0, 270.0, 315.0, 360.0, 405.0, 450.0, 495.0,
+		540.0, 585.0, 630.0, 675.0]" shape="(24,)" standard_name="longitude" units="Unit('degrees')" value_type="float64"/>
+      </coord>
+    </coords>
+    <cellMethods/>
+    <data dtype="float64" shape="(3, 24)" state="loaded"/>
+  </cube>
+</cubes>