TikZ: Drawing edges between subgraphs

Question

I have this:

\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{graphs, graphs.standard}

\begin{document}

\tikz
\graph [simple, nodes={draw, circle, minimum size = .5cm}, clockwise] {
  subgraph C_n [name=inner, radius = 1.5cm, n=3];
  subgraph C_n [name=outer, radius = 3cm, n=4];
};

\end{document}

And now I want to draw single edges from nodes of inner to nodes of outer. How do I do that?

Answer 1

Use the names inner and outer as prefix for the node numbers:

\documentclass[border=3pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{graphs, graphs.standard}

\begin{document}

\begin{tikzpicture}
\graph [simple, nodes={draw, circle, minimum size = .5cm}, clockwise] 
{
  subgraph C_n [name=inner, radius = 1.5cm, n=3];
  subgraph C_n [name=outer, radius = 3cm, n=4];
};
\draw
 (inner 1) -- (outer 2)
 (inner 3) -- (outer 4)
 (inner 2) -- (outer 4)
 (inner 3) -- (outer 1)
 (inner 2) -- (outer 3);
\end{tikzpicture}

\end{document}

The result:

Of course, you can also use the edge path:

\path
 (inner 1) edge (outer 2)
 (inner 3) edge (outer 4)
 (inner 2) edge (outer 4)
 (inner 3) edge (outer 1)
 (inner 2) edge (outer 3);