[R] Adding percentage to Pie Charts

[Gabor Grothendieck]

It might also be nice to be able to align the fans at the left or right,
not just the center.

On 9/23/06, Jim Lemon <jim at bitwrit.com.au> wrote:
> Hi all,
>
> Anupam Tyagi mentioned an interesting idea a few days ago.
>
> "A modification in a pie chart that draws overlapping areas with a
> common start point at the top of the circle, can make is more
> informative than a dot-chart.
> Something like:
> * Start drawing at the top of the circle, as zero (degree/area).
> * Draw the representation of every value starting from the top, as zero,
> representing it as a labled line from the center of the circle to the
> boundary
> (can use colors where possible).
> * Use two lables for the circular axis, inside one for percentages,
> outside for values."
>
> I admit to interpreting this pretty loosely, but I would like to know
> what people think of a "fan plot".
>
> fan.plot<-function(x,edges=200,radius=1,col=NULL,centerpos=pi/2,
>  labels=NULL,...) {
>
>  if (!is.numeric(x) || any(is.na(x) | x<=0))
>   stop("fan.plot: x values must be positive.")
>  # scale the values to a half circle
>  x<-pi*x/sum(x)
>  xorder<-order(x,decreasing=TRUE)
>  nx <- length(x)
>  if (is.null(col)) col<-rainbow(nx)
>  else if(length(col) < nx) col<-rep(col,nx)
>  oldpar<-par(no.readonly=TRUE)
>  par(mar=c(0,0,4,0))
>  plot(0,xlim=c(-1,1),ylim=c(-0.6,1),xlab="",ylab="",type="n",axes=FALSE)
>  lside<--0.8
>  for(i in 1:nx) {
>   n<-edges*x[xorder[i]]/pi
>   t2p<-seq(centerpos-x[xorder[i]],centerpos+x[xorder[i]],length=n)
>   xc<-c(cos(t2p)*radius,0)
>   yc<-c(sin(t2p)*radius,0)
>   polygon(xc,yc,col=col[xorder[i]],...)
>   if(!is.null(labels)) {
>    xpos<-lside*sin(x[xorder[i]])*radius
>    ypos<--i/10
>    text(xpos,ypos,labels[xorder[i]])
>    ytop<-cos(x[xorder[i]])*radius*radius
>    segments(xpos,ypos+1/20,xpos,ytop)
>    lside<--lside
>   }
>   radius<-radius-0.02
>  }
> }
>
> Jim
>
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