SDI {rSDI}

Computes graph or vertex level Spatial Dispersion Index(ces).

Description

If 'flows' is an igraph object then one can avoid supplying the nodes parameter. Alternatively one can supply flows as a data frame and nodes as another.

Usage

SDI(
  flows,
  nodes = NULL,
  distance.calculation = NULL,
  level = "vertex",
  weight.use = "weighted",
  directionality = "undirected",
  variant = NULL,
  alpha = NULL
)

Arguments

flows

A data frame or an igraph object

nodes

if flows are data frame, nodes must be supplied as a data frame. If flows are igraph object then not required

distance.calculation

optional method for distance calculation. 'Haversine' or 'Euclidean'. If not provided and edge distances are not available, distances are calculated by the SDI function.

level

The level to calculate the SDI. 'network' or 'vertex'

weight.use

'weighted', 'unweighted', or 'generalized'

directionality

'undirected', 'in', 'out', or 'all'

variant

Optional. Instead of specifying the level, directionality, and weight separately, the user can just supply a short-code of initial letters of each in that order to this argument, e.g. "vuw" for vertex level, undirected and weighted SDI. If it is a vector each value is treated separetely and multiple indices are computed.

alpha

Optional parameter used for generalized SDI calculations.

Details

To have an SDI computed you can must provide level, weight.use, and directionality parameters. Alternatively the 'variant' parameter can be specified which allows short-codes to indicate all of these three parameters. For example a value of "vui" for variant means a **v**ertex level, **u**ndirected, and **i**nward directed SDI calculation. See the description of these three parameters to figure out possible short codes in a similar fashion.

The function returns an igraph object. If a network level calculation is requested the object will have an 'SDI_...' attribute whose name follows the short codes explained above. If a vertex level calculation is requested each vertex will have a similarly named attribute. For example the graph will have an 'SDI_nuw' attribute if variant is "nuw" (network level, undirected, and weighted). If variant is "vwu" each vertex will have an "SDI_vwu" attribute containing weighted undirected SDI for the vertex. If variant is a vector each value indicates a separate variant to be computed.

Value

An igraph object with SDI attributes added. The class of the object includes 'SDI'.

Examples

SDI(TurkiyeMigration.flows, TurkiyeMigration.nodes, variant="vuw")