Layout algorithm to visualize multilevel networks

layout_as_multilevel(
  g,
  type = "all",
  FUN1,
  FUN2,
  params1 = NULL,
  params2 = NULL,
  ignore_iso = TRUE,
  project2D = TRUE,
  alpha = 35,
  beta = 45
)

layout_igraph_multilevel(
  g,
  type = "all",
  FUN1,
  FUN2,
  params1 = NULL,
  params2 = NULL,
  ignore_iso = TRUE,
  alpha = 35,
  beta = 45,
  circular
)

Arguments

g

igraph object. Must have a vertex attribute "lvl" which is 1 or 2.

type

one of "all", "separate","fix1" or "fix2". see details

FUN1

if type="separate", the layout function to be used for level 1

FUN2

if type="separate", the layout function to be used for level 2

params1

named list of parameters for FUN1

params2

named list of parameters for FUN2

ignore_iso

treatment of isolates within levels. see details

project2D

logical. Defaults to TRUE (project to 2D).

alpha

angle for isometric projection between 0 and 90

beta

angle for isometric projection between 0 and 90

circular

not used

Value

matrix of xy coordinates

Details

The algorithm internally computes a 3D layout where each level is in a separate y-plane. The layout is then projected into 2D via an isometric mapping, controlled by the parameters alpha and beta. It may take some adjusting to alpha and beta to find a good perspective.

If type="all", the layout is computed at once for the complete network. For type="separate", two user specified layout algorithms (FUN1 and FUN2) are used for the levels. The named lists param1 and param2 can be used to set parameters for FUN1 and FUN2. This option helpful for situations where different structural features of the levels should be emphasized.

For type="fix1" and type="fix2" only one of the level layouts is fixed. The other one is calculated by optimizing the inter level ties, such that they are drawn (almost) vertical.

The ignore_iso parameter controls the handling of isolates. If TRUE, nodes without inter level edges are ignored during the layout process and added at the end. If FALSE they are left unchanged

The layout_igraph_* function should not be used directly. It is only used as an argument for plotting with 'igraph'.

Examples

library(igraph) data("multilvl_ex") # compute a layout for the whole network xy <- layout_as_multilevel(multilvl_ex,type = "all", alpha = 25, beta = 45) #compute a layout for each level separately and combine them xy <- layout_as_multilevel(multilvl_ex,type = "separate", FUN1 = layout_as_backbone, FUN2 = layout_with_stress, alpha = 25, beta = 45)