circular = TRUE the nodes will be laid out on the unit circle instead.
In the case where the sort.by attribute is numeric, the numeric values
will be used as the x-position and it is thus possible to have uneven spacing
between the nodes.
layout_igraph_linear(graph, circular, sort.by = NULL, use.numeric = FALSE, offset = pi/2)FALSE.circular = TRUE, where should it begin. Defaults to
pi/2 which is equivalent to 12 o'clock.x, y, circular as
well as any information stored as vertex attributes on the igraph object.
layout_igraph_auto,
  layout_igraph_circlepack,
  layout_igraph_dendrogram,
  layout_igraph_hive,
  layout_igraph_manual,
  layout_igraph_partition,
  layout_igraph_treemap