sna: gplot – R documentation

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gplot

Two-Dimensional Visualization of Graphs

Description

gplot produces a two-dimensional plot of graph g in collection dat. A variety of options are available to control vertex placement, display details, color, etc.

Usage

gplot(dat, g = 1, gmode = "digraph", diag = FALSE, 
    label = NULL, coord = NULL, jitter = TRUE, thresh = 0, 
    thresh.absval=TRUE, usearrows = TRUE, mode = "fruchtermanreingold", 
    displayisolates = TRUE, interactive = FALSE, interact.bycomp = FALSE,
    xlab = NULL, ylab = NULL, xlim = NULL, ylim = NULL, pad = 0.2, 
    label.pad = 0.5, displaylabels = !is.null(label), boxed.labels = FALSE, 
    label.pos = 0, label.bg = "white", vertex.enclose = FALSE, 
    vertex.sides = NULL, vertex.rot = 0, arrowhead.cex = 1, label.cex = 1, 
    loop.cex = 1, vertex.cex = 1, edge.col = 1, label.col = 1, 
    vertex.col = NULL, label.border = 1, vertex.border = 1, edge.lty = NULL,
    edge.lty.neg=2, label.lty = NULL, vertex.lty = 1, edge.lwd = 0, 
    label.lwd = par("lwd"), edge.len = 0.5, edge.curve = 0.1, 
    edge.steps = 50, loop.steps = 20, object.scale = 0.01, uselen = FALSE, 
    usecurve = FALSE, suppress.axes = TRUE, vertices.last = TRUE, 
    new = TRUE, layout.par = NULL, ...)

Arguments

`dat`	a graph or set thereof. This data may be valued.
`g`	integer indicating the index of the graph which is to be plotted. By default, `g==1`.
`gmode`	String indicating the type of graph being evaluated. `"digraph"` indicates that edges should be interpreted as directed; `"graph"` indicates that edges are undirected; `"twomode"` indicates that data should be interpreted as two-mode (i.e., rows and columns are distinct vertex sets). `gmode` is set to `"digraph"` by default.
`diag`	boolean indicating whether or not the diagonal should be treated as valid data. Set this true if and only if the data can contain loops. `diag` is `FALSE` by default.
`label`	a vector of vertex labels, if desired; defaults to the vertex index number.
`coord`	user-specified vertex coordinates, in an NCOL(dat)x2 matrix. Where this is specified, it will override the `mode` setting.
`jitter`	boolean; should the output be jittered?
`thresh`	real number indicating the lower threshold for tie values. Only ties of value >`thresh` (by default in absolute value - see `thresh.absval`)are displayed. By default, `thresh`=0.
`thresh.absval`	boolean; should the absolute value of edge weights be used when thresholding? (Defaults to TRUE; setting to FALSE leads to thresholding by signed weights.)
`usearrows`	boolean; should arrows (rather than line segments) be used to indicate edges?
`mode`	the vertex placement algorithm; this must correspond to a `gplot.layout` function.
`displayisolates`	boolean; should isolates be displayed?
`interactive`	boolean; should interactive adjustment of vertex placement be attempted?
`interact.bycomp`	boolean; if `interactive==TRUE`, should all vertices in the component be moved?
`xlab`	x axis label.
`ylab`	y axis label.
`xlim`	the x limits (min, max) of the plot.
`ylim`	the y limits of the plot.
`pad`	amount to pad the plotting range; useful if labels are being clipped.
`label.pad`	amount to pad label boxes (if `boxed.labels==TRUE`), in character size units.
`displaylabels`	boolean; should vertex labels be displayed?
`boxed.labels`	boolean; place vertex labels within boxes?
`label.pos`	position at which labels should be placed, relative to vertices. `0` results in labels which are placed away from the center of the plotting region; `1`, `2`, `3`, and `4` result in labels being placed below, to the left of, above, and to the right of vertices (respectively); and `label.pos>=5` results in labels which are plotted with no offset (i.e., at the vertex positions).
`label.bg`	background color for label boxes (if `boxed.labels==TRUE`); may be a vector, if boxes are to be of different colors.
`vertex.enclose`	boolean; should vertices be enclosed within circles? (Can increase legibility for polygonal vertices.)
`vertex.sides`	number of polygon sides for vertices; may be given as a vector, if vertices are to be of different types. By default, 50 sides are used (or 50 and 4, for two-mode data).
`vertex.rot`	angle of rotation for vertices (in degrees); may be given as a vector, if vertices are to be rotated differently.
`arrowhead.cex`	expansion factor for edge arrowheads.
`label.cex`	character expansion factor for label text.
`loop.cex`	expansion factor for loops; may be given as a vector, if loops are to be of different sizes.
`vertex.cex`	expansion factor for vertices; may be given as a vector, if vertices are to be of different sizes.
`edge.col`	color for edges; may be given as a vector or adjacency matrix, if edges are to be of different colors.
`label.col`	color for vertex labels; may be given as a vector, if labels are to be of different colors.
`vertex.col`	color for vertices; may be given as a vector, if vertices are to be of different colors. By default, red is used (or red and blue, for two-mode data).
`label.border`	label border colors (if `boxed.labels==TRUE`); may be given as a vector, if label boxes are to have different colors.
`vertex.border`	border color for vertices; may be given as a vector, if vertex borders are to be of different colors.
`edge.lty`	line type for (positive weight) edges; may be given as a vector or adjacency matrix, if edges are to have different line types.
`edge.lty.neg`	line type for negative weight edges, if any; may be given as per `edge.lty`.
`label.lty`	line type for label boxes (if `boxed.labels==TRUE`); may be given as a vector, if label boxes are to have different line types.
`vertex.lty`	line type for vertex borders; may be given as a vector or adjacency matrix, if vertex borders are to have different line types.
`edge.lwd`	line width scale for edges; if set greater than 0, edge widths are scaled by `edge.lwd*dat`. May be given as a vector or adjacency matrix, if edges are to have different line widths.
`label.lwd`	line width for label boxes (if `boxed.labels==TRUE`); may be given as a vector, if label boxes are to have different line widths.
`edge.len`	if `uselen==TRUE`, curved edge lengths are scaled by `edge.len`.
`edge.curve`	if `usecurve==TRUE`, the extent of edge curvature is controlled by `edge.curv`. May be given as a fixed value, vector, or adjacency matrix, if edges are to have different levels of curvature.
`edge.steps`	for curved edges (excluding loops), the number of line segments to use for the curve approximation.
`loop.steps`	for loops, the number of line segments to use for the curve approximation.
`object.scale`	base length for plotting objects, as a fraction of the linear scale of the plotting region. Defaults to 0.01.
`uselen`	boolean; should we use `edge.len` to rescale edge lengths?
`usecurve`	boolean; should we use `edge.curve`?
`suppress.axes`	boolean; suppress plotting of axes?
`vertices.last`	boolean; plot vertices after plotting edges?
`new`	boolean; create a new plot? If `new==FALSE`, vertices and edges will be added to the existing plot.
`layout.par`	parameters to the `gplot.layout` function specified in `mode`.
`...`	additional arguments to `plot`.

Details

gplot is the standard network visualization tool within the sna library. By means of clever selection of display parameters, a fair amount of display flexibility can be obtained. Graph layout – if not specified directly using coord – is determined via one of the various available algorithms. These should be specified via the mode argument; see gplot.layout for a full list. User-supplied layout functions are also possible – see the aforementioned man page for details.

Note that where gmode=="twomode", the supplied two-mode network is converted to bipartite form prior to computing coordinates (if not in that form already). vertex.col or other settings may be used to differentiate row and column vertices – by default, row vertices are drawn as red circles, and column vertices are rendered as blue squares. If interactive==TRUE, then the user may modify the initial graph layout by selecting an individual vertex and then clicking on the location to which this vertex is to be moved; this process may be repeated until the layout is satisfactory. If interact.bycomp==TRUE as well, the vertex and all other vertices in the same component as that vertex are moved together.

Value

A two-column matrix containing the vertex positions as x,y coordinates.

Author(s)

Carter T. Butts buttsc@uci.edu

Alex Montgomery ahm@reed.edu

References

Wasserman, S. and Faust, K. (1994) Social Network Analysis: Methods and Applications. Cambridge: Cambridge University Press.

Examples

gplot(rgraph(5))               #Plot a random graph
gplot(rgraph(5),usecurv=TRUE)  #This time, use curved edges
gplot(rgraph(5),mode="mds")    #Try an alternative layout scheme

#A colorful demonstration...
gplot(rgraph(5,diag=TRUE),diag=TRUE,vertex.cex=1:5,vertex.sides=3:8,
    vertex.col=1:5,vertex.border=2:6,vertex.rot=(0:4)*72,
    displaylabels=TRUE,label.bg="gray90")

sna

Tools for Social Network Analysis

v2.6

GPL (>= 2)

Authors

Carter T. Butts [aut, cre, cph]

Initial release

2020-10-5