Misc Tweaks

Start documenting Graph.
Use existing graph layout  in FindSpanningTree
RandomGraph doc fix.

Author: rocky

pymathics/graph/__main__.py

@@ -760,7 +760,7 @@ class DirectedEdge(Builtin):
 class UndirectedEdge(Builtin):
     """
     <dl>
-    <dt>'UndirectedEdge[$u$, $v$]'
+      <dt>'UndirectedEdge[$u$, $v$]'
       <dd>an undirected edge between $u$ and $v$.
     </dl>
 
@@ -779,6 +779,16 @@ class UndirectedEdge(Builtin):
 
 class GraphAtom(AtomBuiltin):
     """
+    <dl>
+      <dt>'Graph[{$e1, $e2, ...}]'
+      <dd>returns a graph with edges $e_j$.
+    </dl>
+
+    <dl>
+      <dt>'Graph[{v1, v2, ...}, {$e1, $e2, ...}]'
+      <dd>returns a graph with vertices $v_i$ and edges $e_j$.
+    </dl>
+
     >> Graph[{1->2, 2->3, 3->1}]
      = -Graph-
 

pymathics/graph/algorithms.py

@@ -112,6 +112,11 @@ def apply(self, graph, expression, evaluation, options):
             # FIXME: put in edge to Graph conversion function?
             edges = [Expression("UndirectedEdge", u, v) for u, v in nx.minimum_spanning_edges(graph.G, data=False)]
             g = _create_graph(edges, [None] * len(edges), options)
+            if not hasattr(g.G, "graph_layout"):
+                if hasattr(graph.G, "graph_layout"):
+                    g.G.graph_layout = graph.G.graph_layout
+                else:
+                    g.G.graph_layout = "tree"
             return g
 
 class PlanarGraphQ(_NetworkXBuiltin):

pymathics/graph/generators.py

@@ -530,7 +530,7 @@ class RandomGraph(_NetworkXBuiltin):
       <dt>'RandomGraph[{$n$, $m$}]'
       <dd>Returns a pseudorandom graph with $n$ vertices and $m$ edges.
 
-      <dt>'RandomGraph[$n$, $m$, $k$]'
+      <dt>'RandomGraph[{$n$, $m$}, $k$]'
       <dd>Returns list of $k$ RandomGraph[{$n$, $m$}].
     </dl>
     """