

   PPrreettttyy BBrreeaakkppooiinnttss

        pretty(x, n=5, shrink.sml = 2^-3))

   AArrgguummeennttss::

          x: numeric vector

          n: integer giving the desired number of values.

   shrink.sml: numeric factor, positive (ideally a small power
             of 2), by a which a default scale is shrunk, in
             the case when `range(x)' is ``very small''.

   VVaalluuee::

        a numeric sequence of about `n' equally spaced nice
        values which cover the range of the values in `x'.  The
        values are chosen so that they are 1, 2 or 5 times a
        power of 10.

   EExxaammpplleess::

        pretty(1:15)
        pretty(1:15 * 2)
        pretty(1:20)
        pretty(1:20, n=2)
        pretty(1:20, n=10)

        ##-- more bizarre, using ``shrink.sml'':
        pretty(2)
        pretty(1.234e100)
        pretty(pi)
        pretty(1001.1001)
        pretty(1001.1001, shrink = 1)
        for(k in 5:11) {cat("k=",k,": "); print(pretty(101 + c(0, pi*10^-k)))}
        for(k in -7:3)
          cat("shrink=",formatC(2^k,wid=9),":",
              formatC(pretty(1001.1001, shrink = 2^k), wid=6),"\n")

