Displays an input graph (and associated vector) as a "target diagram," with vertices restricted to lie at fixed radii from the origin. Such displays are useful ways of representing vertex characteristics and/or local structural properties for graphs of small to medium size.

```
gplot.target(dat, x, circ.rad = (1:10)/10, circ.col = "blue",
circ.lwd = 1, circ.lty = 3, circ.lab = TRUE, circ.lab.cex = 0.75,
circ.lab.theta = pi, circ.lab.col = 1, circ.lab.digits = 1,
circ.lab.offset = 0.025, periph.outside = FALSE,
periph.outside.offset = 1.2, ...)
```

dat

an input graph.

x

a vector of vertex properties to be plotted (must match the dimensions of `dat`

).

circ.rad

radii at which to draw reference circles.

circ.col

reference circle color.

circ.lwd

reference circle line width.

circ.lty

reference circle line type.

circ.lab

boolean; should circle labels be displayed?

circ.lab.cex

expansion factor for circle labels.

circ.lab.theta

angle at which to draw circle labels.

circ.lab.col

color for circle labels.

circ.lab.digits

digits to display for circle labels.

circ.lab.offset

offset for circle labels.

periph.outside

boolean; should "peripheral" vertices be drawn together beyond the normal vertex radius?

periph.outside.offset

radius at which "peripheral" vertices should be drawn if `periph.outside==TRUE`

.

…

additional arguments to `gplot`

.

A two-column matrix of vertex positions (generated by `gplot.layout.target`

)

`gplot.target`

is a front-end to `gplot`

which implements the target diagram layout of Brandes et al. (2003). This layout seeks to optimize various aesthetic criteria, given the constraint that all vertices lie at fixed radii from the origin (set by `x`

). One important feature of this algorithm is that vertices which belong to mutual dyads (described by Brandes et al. as ``core'' vertices) are treated differently from vertices which do not (``peripheral'' vertices). Layout is optimized for core vertices prior to placing peripheral vertices; thus, the result may be misleading if mutuality is not a salient characteristic of the data.

The layout for `gplot.target`

is handled by `gplot.layout.target`

; additional parameters are specied on the associated manual page. Standard arguments may be passed to `gplot`

, as well.

Brandes, U.; Kenis, P.; and Wagner, D. (2003). ``Communicating Centrality in Policy Network Drawings.'' *IEEE Transactions on Visualization and Computer Graphics,* 9(2):241-253.

```
# NOT RUN {
#Generate a random graph
g<-rgraph(15)
#Produce a target diagram, centering by betweenness
gplot.target(g,betweenness(g))
# }
```

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