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piechart(p [,start:p0] [,labels:labs] [,rlab:r1 [, rval:r2]\
  [, xwidth:w] [,graphics keyword phrases]), REAL vector p with p[i] >=
  0, p0 >= 0, REAL scalar, CHARACTER vector labs, REAL scalars r1 > 0,
  r2 > 0, w > 0

Keywords: distribution graphs
piechart(p) draws a pie chart of data in REAL vector p which should
have no MISSING values and satisfy min(p) >= 0.  The chart is drawn in
a circle with radius 1.

Usually p is a vector of proportions (sum(p) = 1) or percentages
(sum(p) = 100), but this is not required.  What is actually drawn is a
pie chart with sector angles computed from the proportions p1 =
p/sum(p).  The angle defining sector I of the pie chart, going
clockwise around the circle is 360*p1[I] degrees.  By default, the
starting edge of sector 1 is vertical.  Each sector is is labelled by
sector number, from 1 to nrows(p).

There several optional keywords.

  piechart(p, start:p0 [,other keywords]) where p0 is a REAL scalar
  draws a pie chart with the starting sector edge located p0 of a cycle
  (abs(p0) <= 1) or p0 percent of a cycle (abs(p0) > 1) around the
  circle from the vertical.  For instance, with p0 = .25 or 25, the
  starting sector edge is 90 degrees clockwise from the vertical.
  'start' can be used with other keywords.

  piechart(p, labels:labs [,other keywords]), where labs is a CHARACTER
  vector with length(labs) = length(p), labels sector I with labs[I].
  You can suppress sector labelling with labels:"".

  piechart(p, rlab:r1 [,labels:labs] [,other keywords]) puts sector
  labels at radius r1 > 0 from the pie center.  Usually r1 < 1.  The
  default radius is .9.

  piechart(p, rval:r2 [,other keywords]), prints p[I] at radius r2 > 0
  in sector I, I = 1, ..., length(p).  Usually r2 < 1.  This allows you
  to label sectors both with a descriptive tag and the value of the

  piechart(p, xwidth:w [other keywords]) includes 'xmin:-w/2,xmax:w/2'
  in the argument list of the plotting commands that draw the pie
  chart.  You need to use 'xwidth' only when the plot without it looks
  like an ellipse instead of a circle.  The default is 'xwidth:3.2'.

You can also use many of the usual graphics keywords like 'xlab',
'ylab', 'title' and 'window'.  See topic 'graph_keys'.

If you don't like the default labeling, you may be able to use Mouse()
and addstrings() to position labels more to your liking.  See Mouse()
and addstrings().

Gary Oehlert 2003-01-15