MAINT: Add support for planar layout from NX (#700)

* MAINT: Add support for planar layout from NX

* Update NX user guide with a planar layout example

* clean up metadata

* py2.7 doesn't like underscores in numerics

examples/user_guide/NetworkX.ipynb

@@ -42,6 +42,16 @@
     "spring + shell"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "H = nx.triangular_lattice_graph(1, 20)\n",
+    "hvnx.draw_planar(H, node_color='green', edge_color='brown')"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

hvplot/networkx.py

@@ -582,3 +582,22 @@ def draw_spring(G, **kwargs):
        Graph element or Graph and Labels
     """
     return draw(G, nx.spring_layout, **kwargs)
+
+def draw_planar(G, **kwargs):
+    """Draw networkx graph with planar layout.
+
+    Parameters
+    ----------
+    G : graph
+       A networkx graph
+    kwargs : optional keywords
+       See hvplot.networkx.draw() for a description of optional
+       keywords, with the exception of the pos parameter which is not
+       used by this function.
+
+    Returns
+    -------
+    graph : holoviews.Graph or holoviews.Overlay
+       Graph element or Graph and Labels
+    """
+    return draw(G, nx.planar_layout, **kwargs)

hvplot/ui.py

@@ -24,7 +24,7 @@
 ]
 GEO_TILES = list(tile_sources)
 AGGREGATORS = [None, 'count', 'min', 'max', 'mean', 'sum', 'any']
-MAX_ROWS = 10_000
+MAX_ROWS = 10000
 
 
 class Controls(Viewer):