R's pretty algorithm implemented in R

rpretty(dmin, dmax, m = 6, n = floor(m) - 1,
    min.n = n%/%3, shrink.sml = 0.75, high.u.bias = 1.5,
    u5.bias = 0.5 + 1.5 * high.u.bias)

Arguments

dmin: minimum of the data range
dmax: maximum of the data range
m: number of axis labels
n: number of axis intervals (specify one of m or n)
min.n: nonnegative integer giving the minimal number of intervals. If min.n == 0, pretty(.) may return a single value.
shrink.sml: positive numeric by a which a default scale is shrunk in the case when range(x) is very small (usually 0).
high.u.bias: non-negative numeric, typically > 1. The interval unit is determined as {1,2,5,10} times b, a power of 10. Larger high.u.bias values favor larger units.
u5.bias: non-negative numeric multiplier favoring factor 5 over 2. Default and 'optimal': u5.bias = .5 + 1.5*high.u.bias.

vector of axis label locations

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.