gplot {sna}R Documentation

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 = c(1:dim(dat)[2]), coord = NULL, jitter = TRUE, thresh = 0,
    usearrows = TRUE, mode = "fruchtermanreingold", 
    displayisolates = TRUE, interactive = FALSE, xlab = NULL, 
    ylab = NULL, xlim = NULL, ylim = NULL, pad = 0.2, label.pad = 0.5,
    displaylabels = !missing(label), boxed.labels = TRUE, 
    label.pos = 0, label.bg = "white", vertex.sides = 8, vertex.rot = 0,
    arrowhead.cex = 1, label.cex = 1, loop.cex = 1, vertex.cex = 1,
    edge.col = 1, label.col = 1, vertex.col = 2, label.border = 1,
    vertex.border = 1, edge.lty = 1, 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 bimodal (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 are displayed. By default, thresh=0.
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?
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.sides number of polygon sides for vertices; may be given as a vector, if vertices are to be of different types.
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.
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 edge borders; may be given as a vector or adjacency matrix, if edge borders are to have different line types.
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 matrix is converted to bipartite adjacency form prior to computing coordinates. 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.

Value

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

Author(s)

Carter T. Butts buttsc@uci.edu

Alex Montgomery ahm@stanford.edu

References

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

See Also

plot, gplot.layout

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")
    

[Package sna version 1.5 Index]