Important:The networks package has been deprecated. Use the superseding package GraphTheoryinstead.

If a single argument G is passed then a table is returned.

If a single edge e is passed the either the head of e or NULL is returned depending on whether or not e is directed.

If a set of edges eset is passed then a set or list of head vertices is returned.

This routine is normally loaded via the command with(networks) but may also be referenced using the full name networks[head](...).

$\mathrm{with}\left(\mathrm{networks}\right)\:$

$\mathrm{new}\left(G\right)\:$

$\mathrm{addvertex}\left(1\,2\,3\,4\,5\,G\right)\:$

$\mathrm{addedge}\left(\left[\left[1\,2\right]\,\left[2\,3\right]\,\left[3\,4\right]\,\left[4\,5\right]\right]\,G\right)$

$\mathrm{e1},\mathrm{e2},\mathrm{e3},\mathrm{e4}$

$\mathrm{addedge}\left(\left\{1\,5\right\}\,G\right)$

$\mathrm{e5}$

$\mathrm{head}\left(\,G\right)$

$\mathrm{head}\left(G\right)$

$table\left(\left[\mathrm{e3}=4\,\mathrm{e1}=2\,\mathrm{e2}=3\,\mathrm{e4}=5\right]\right)$

$\mathrm{head}\left(\left[\mathrm{e1}\,\mathrm{e2}\,\mathrm{e5}\right]\,G\right)$

$\left[2\,3\right]$