Display a 3D pie chart

Displays a 3D pie chart with optional labels.

Usage

pie3D(x,edges=NA,radius=1,height=0.1,theta=pi/6,start=0,border=par("fg"),
  col=NULL,labels=NULL,labelpos=NULL,labelcol=par("fg"),labelcex=1.5,
  sector.order=NULL,explode=0,shade=0.8,mar=c(4,4,4,4),pty="s",...)

Arguments

x: a numeric vector for which each value will be a sector
edges: the number of lines forming an ellipse
radius: the radius of the pie in user units
height: the height of the pie in user units
theta: The angle of viewing in radians
start: The angle at which to start drawing sectors.
border: The color of the sector border lines
col: The colors of the sectors
labels: Optional labels for each sector
labelpos: Optional positions for the labels (see examples)
labelcol: The color of the labels
labelcex: The character expansion factor for the labels
sector.order: Allows the operator to specify the order in which the sectors are drawn.
explode: The amount to "explode" the pie in user units
shade: If > 0 and < 1, the proportion to reduce the brightness of the sector color to get a better 3D effect.
mar: Margins around the pie.
pty: Whether to force a square plot region or not. (see Details)
...: graphical parameters passed to plot

Value

The bisecting angle of the sectors in radians.

Details

pie3D scales the values in x so that they total 2*pi, dropping zeros and NAs. It then displays an empty plot, calculates the sequence for drawing the sectors and calls draw.tilted.sector to draw each sector. If labels are supplied, it will call pie3D.label to place these outside each sector. If supplied, the number of labels, label positions and sector colors must be at least equal to the number of values in x. If the labels are long, it may help to reduce the radius of the pie or change the position as in the example below.

In order to make the dimensions of the pie reasonably accurate, a square plot region (pty="s") is the default. If pty is set to "m", the user can change the margins, usually resulting in a non-square plot area. This will probably distort the pie somewhat.

Note

Due to the somewhat primitive method used to draw sectors, a sector that extends beyond both pi/2 and 3*pi/2 radians in either direction may not display properly. Setting start to pi/2 will often fix this, but the user may have to adjust start and the order of sectors in extreme cases. The argument sector.order allows the user to specify a vector of integers that will override the calculation of the order in which the sectors are drawn. This is usually necessary when a very large sector that extends past 3*pi/2 is overlapped by a smaller sector next to it. As a last resort, the user can try setting explode to zero. This only draws the top and outer sides of each sector.

Also due to the sector drawing method, setting theta to values smaller than about pi/8 or larger than about pi/4 will produce obviously misaligned sectors.

Contributed fixes and improvements: thanks to Jesse Brown for the "shade" fix and Qinghua Zhao for alerting me to the problem with labels and margins

Author

Jim Lemon

Examples

 pieval<-c(2,4,6,8)
 pielabels<-
  c("We hate\n pies","We oppose\n  pies","We don't\n  care","We just love pies")
 # grab the radial positions of the labels
 lp<-pie3D(pieval,radius=0.9,labels=pielabels,explode=0.1,main="3D PIE OPINIONS")

 # lengthen the last label and move it to the left
 pielabels[4]<-"We cannot survive without our pies"
 lp[4]<-4.8
 # specify some new colors
 pie3D(pieval,radius=0.9,labels=pielabels,explode=0.1,main="3D PIE OPINIONS",
  col=c("brown","#ddaa00","pink","#dd00dd"),labelpos=lp)