Grid conserves subclasses of ndarray (#56)

- uses solution proposed by @AstroMike (np.asanyarray())
- fix #56
- add test (with np.ma.MaskedArray)
- update CHANGELOG

CHANGELOG

@@ -24,6 +24,8 @@ The rules for this file:
   * Added missing floordivision to Grid (PR #53)
   * fix test on ARM (#51)
   * fix incorrect reading of ncstart and nrstart in CCP4 (#57)
+  * fix that arithemtical operations broke inheritance (#56)
+  * fix so that subclasses of ndarray are retained on input (#56)
 
   Changes (do not affect user)
 

gridData/core.py

@@ -126,13 +126,13 @@ def __init__(self, grid=None, edges=None, origin=None, delta=None,
             self.load(grid)
         elif not (grid is None or edges is None):
             # set up from histogramdd-type data
-            self.grid = numpy.asarray(grid)
+            self.grid = numpy.asanyarray(grid)
             self.edges = edges
             self._update()
         elif not (grid is None or origin is None or delta is None):
             # setup from generic data
-            origin = numpy.asarray(origin)
-            delta = numpy.asarray(delta)
+            origin = numpy.asanyarray(origin)
+            delta = numpy.asanyarray(delta)
             if len(origin) != grid.ndim:
                 raise TypeError(
                     "Dimension of origin is not the same as grid dimension.")
@@ -148,7 +148,7 @@ def __init__(self, grid=None, edges=None, origin=None, delta=None,
             self.edges = [origin[dim] +
                           (numpy.arange(m + 1) - 0.5) * delta[dim]
                           for dim, m in enumerate(grid.shape)]
-            self.grid = numpy.asarray(grid)
+            self.grid = numpy.asanyarray(grid)
             self._update()
         else:
             # empty, must manually populate with load()
@@ -709,7 +709,7 @@ def ndmeshgrid(*arrs):
     for i, arr in enumerate(arrs):
         slc = [1] * dim
         slc[i] = lens[i]
-        arr2 = numpy.asarray(arr).reshape(slc)
+        arr2 = numpy.asanyarray(arr).reshape(slc)
         for j, sz in enumerate(lens):
             if j != i:
                 arr2 = arr2.repeat(sz, axis=j)

gridData/tests/test_grid.py

@@ -9,6 +9,9 @@
 
 from gridData import Grid
 
+def f_arithmetic(g):
+    return g + g - 2.5 * g / (g + 5.3)
+
 @pytest.fixture(scope="class")
 def data():
     d = dict(
@@ -148,11 +151,20 @@ class DerivedGrid(Grid):
 
     dg = DerivedGrid(data['griddata'], origin=data['origin'],
                      delta=data['delta'])
-    result = dg + dg - 2.5 * dg / (dg + 5.3)
+    result = f_arithmetic(dg)
 
     assert isinstance(result, DerivedGrid)
 
-    g = data['grid']
-    ref = g + g - 2.5 * g / (dg + 5.3)
+    ref = f_arithmetic(data['grid'])
     assert_almost_equal(result.grid, ref.grid)
 
+def test_anyarray(data):
+    ma = np.ma.MaskedArray(data['griddata'])
+    mg = Grid(ma, origin=data['origin'], delta=data['delta'])
+
+    assert isinstance(mg.grid, ma.__class__)
+
+    result = f_arithmetic(mg)
+    ref = f_arithmetic(data['grid'])
+
+    assert_almost_equal(result.grid, ref.grid)