From 84f25c460f698dc37254c168b3e9c733a4a8e866 Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <P.Rudiger@ed.ac.uk>
Date: Sun, 5 Feb 2017 22:37:22 +0000
Subject: [PATCH 1/2] Merge dynamic dimension values

---
 holoviews/core/spaces.py    |  3 ++-
 holoviews/core/traversal.py |  4 ++--
 holoviews/core/util.py      | 17 +++++++++++++++++
 tests/testutils.py          | 18 +++++++++++++++++-
 4 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/holoviews/core/spaces.py b/holoviews/core/spaces.py
index 5480a33f7b..58b50a6d5b 100644
--- a/holoviews/core/spaces.py
+++ b/holoviews/core/spaces.py
@@ -171,7 +171,8 @@ def __mul__(self, other):
             # dimension labels for the new view
             self_in_other = self_set.issubset(other_set)
             other_in_self = other_set.issubset(self_set)
-            dimensions = self.kdims
+            dims = [other.kdims, self.kdims] if self_in_other else [self.kdims, other.kdims]
+            dimensions = util.merge_dimensions(dims)
 
             if self_in_other and other_in_self: # superset of each other
                 keys = self._dimension_keys() + other._dimension_keys()
diff --git a/holoviews/core/traversal.py b/holoviews/core/traversal.py
index 896e69f708..c377e178ae 100644
--- a/holoviews/core/traversal.py
+++ b/holoviews/core/traversal.py
@@ -8,6 +8,7 @@
 from operator import itemgetter
 
 from .dimension import Dimension, OrderedDict
+from .util import merge_dimensions
 
 try:
     import itertools.izip as zip
@@ -56,8 +57,7 @@ def unique_dimkeys(obj, default_dim='Frame'):
     subset = all(g1 <= g2 or g1 >= g2 for g1 in dgroups for g2 in dgroups)
     # Find unique keys
     if subset:
-        dims = OrderedDict([(dim.name, dim) for dim_group in dim_groups
-                            for dim in dim_group]).values()
+        dims = merge_dimensions(dim_groups)
         all_dims = sorted(dims, key=lambda x: dim_groups[0].index(x))
     else:
         all_dims = [default_dim]
diff --git a/holoviews/core/util.py b/holoviews/core/util.py
index 9223f01077..e5a071cc7b 100644
--- a/holoviews/core/util.py
+++ b/holoviews/core/util.py
@@ -608,6 +608,23 @@ def python2sort(x,key=None):
     return itertools.chain.from_iterable(sorted(group, key=key) for group in groups)
 
 
+def merge_dimensions(dimensions_list):
+    """
+    Merges lists of fully or partially overlapping dimensions by
+    combining their values.
+    """
+    dvalues = defaultdict(list)
+    dimensions = []
+    for dims in dimensions_list:
+        for d in dims:
+            dvalues[d.name].append(d.values)
+            if d not in dimensions:
+                dimensions.append(d)
+    dvalues = {k: list(unique_iterator(itertools.chain(*vals)))
+               for k, vals in dvalues.items()}
+    return [d(values=dvalues.get(d.name, [])) for d in dimensions]
+
+
 def dimension_sort(odict, kdims, vdims, categorical, key_index, cached_values):
     """
     Sorts data by key using usual Python tuple sorting semantics
diff --git a/tests/testutils.py b/tests/testutils.py
index 7fc7b4b656..5aabb9954c 100644
--- a/tests/testutils.py
+++ b/tests/testutils.py
@@ -14,7 +14,10 @@
 except:
     pd = None
 
-from holoviews.core.util import sanitize_identifier_fn, find_range, max_range, wrap_tuple_streams, deephash
+from holoviews.core.util import (
+    sanitize_identifier_fn, find_range, max_range, wrap_tuple_streams,
+    deephash, merge_dimensions
+)
 from holoviews import Dimension
 from holoviews.streams import PositionXY
 from holoviews.element.comparison import ComparisonTestCase
@@ -447,3 +450,16 @@ def test_no_streams_two_stream_substitution(self):
                                     [Dimension('x'), Dimension('y')],
                                     [PositionXY(x=0,y=5)])
         self.assertEqual(result, (0,5))
+
+
+class TestMergeDimensions(unittest.TestCase):
+
+    def test_merge_dimensions(self):
+        dimensions = merge_dimensions([[Dimension('A')], [Dimension('A'), Dimension('B')]])
+        self.assertEqual(dimensions, [Dimension('A'), Dimension('B')])
+
+    def test_merge_dimensions_with_values(self):
+        dimensions = merge_dimensions([[Dimension('A', values=[0, 1])],
+                                       [Dimension('A', values=[1, 2]), Dimension('B')]])
+        self.assertEqual(dimensions, [Dimension('A'), Dimension('B')])
+        self.assertEqual(dimensions[0].values, [0, 1, 2])

From f66ec437186335cca7b62ad69bb22c187e886656 Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <P.Rudiger@ed.ac.uk>
Date: Mon, 6 Feb 2017 17:30:23 +0000
Subject: [PATCH 2/2] Added doctest to merge_dimensions utility

---
 holoviews/core/util.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/holoviews/core/util.py b/holoviews/core/util.py
index e5a071cc7b..1800d45811 100644
--- a/holoviews/core/util.py
+++ b/holoviews/core/util.py
@@ -611,7 +611,16 @@ def python2sort(x,key=None):
 def merge_dimensions(dimensions_list):
     """
     Merges lists of fully or partially overlapping dimensions by
-    combining their values.
+    merging their values.
+
+    >>> from holoviews import Dimension
+    >>> dim_list = [[Dimension('A', values=[1, 2, 3]), Dimension('B')],
+    ...             [Dimension('A', values=[2, 3, 4])]]
+    >>> dimensions = merge_dimensions(dim_list)
+    >>> dimensions
+    [Dimension('A'), Dimension('B')]
+    >>> dimensions[0].values
+    [1, 2, 3, 4]
     """
     dvalues = defaultdict(list)
     dimensions = []