plotrix (version 2.5-2)

fan.plot: Display a fan plot.

Description

Displays numerical values as the arcs of overlapping sectors.

Usage

fan.plot(x,edges=200,radius=1,col=NULL,align.at=NULL,max.span=NULL,
  labels=NULL,labelpos=NULL,label.radius=1.2,align="left",shrink=0.02,
  main="",ticks=NULL,include.sumx=FALSE,...)

Arguments

x

Vector of numbers.

edges

The number of edges with which to draw a circle.

radius

The radius of the sectors.

col

The colors with which to fill the sectors.

align.at

Where to align the sectors (see Details).

max.span

The angle of the maximal sector in radians. The default is to scale x so that it sums to 2*pi.

labels

Labels placed around the sector arcs.

labelpos

Optional circumferential positions for the labels.

label.radius

How far away from the sectors the labels will be placed. May be a vector with a radius for each label.

align

Position of the alignment of sectors (see Details).

shrink

How much to shrink each successive sector in user units.

main

Optional title for the plot.

ticks

The number of ticks that would appear if the sectors were on a pie chart. Default is no ticks, TRUE gives the number of ticks equal to the integer sum of x, which is fairly sensible if x is a vector of integers.

include.sumx

Whether to include the sum of all x values as the largest sector.

...

Additional arguments passed to polygon.

Value

• The circumferential positions of the labels in radians. These are returned in order of decreasing size of the values plotted.

Details

The fan plot is a variant of the pie chart that places the sectors "on top" of each other from the largest to the smallest. By default, the largest sector is centered with its circumferential arc upwards, giving the plot the appearance of a folding fan. Passing a value for align.at will place the point of alignment at that angle in radians. The sectors may be aligned at either the left or right edges or in the center. Note that align must be one of left right or center. Each successive sector is radially "shrunk" by a constant amount so that two equal sectors will both be visible. In cases where there are several segments with very small differences, the labels may be crowded. There is a simple routine in the function to spread out crowded labels, but it may not be sufficient for severe crowding. By capturing the return value and manually altering the label positions, the crowded labels can be separated. This new vector of positions may then be passed as labelpos. The calculation of sectors tries to ensure that they are circular. Thus there will be white space if the plotting device dimensions are not proportional to the size of the plot. The user must adjust the dimensions of the plotting device to get the correct appearance.

See Also

floating.pie

Examples

# IUCN counts of threatened species by geographical area
 iucn.df<-data.frame(area=c("Africa","Asia","Europe","N&C America",
  "S America","Oceania"),threatened=c(5994,7737,1987,4716,5097,2093))
 fan.plot(iucn.df$threatened,
  labels=paste(iucn.df$area,iucn.df$threatened,sep="-"),
  main="Threatened species by geographical area",ticks=276)
 # expand the plot to a semicircle
 fan.plot(iucn.df$threatened,max.span=pi,
  labels=paste(iucn.df$area,iucn.df$threatened,sep="-"),
  main="Threatened species by geographical area",ticks=276)
 # expand further to 3/4 of a circle
 fan.plot(iucn.df$threatened,max.span=1.5*pi,
  labels=paste(iucn.df$area,iucn.df$threatened,sep="-"),
  main="Threatened species by geographical area",ticks=276)