wilkinson: Wilkinson's labeling algorithm

View source: R/labeling.R

wilkinsonR Documentation

Wilkinson's labeling algorithm


Wilkinson's labeling algorithm


  wilkinson(dmin, dmax, m,
    Q = c(1, 5, 2, 2.5, 3, 4, 1.5, 7, 6, 8, 9),
    mincoverage = 0.8,
    mrange = max(floor(m/2), 2):ceiling(6 * m))



minimum of the data range


maximum of the data range


number of axis labels


set of nice numbers


minimum ratio between the the data range and the labeling range, controlling the whitespace around the labeling (default = 0.8)


range of m, the number of tick marks, that should be considered in the optimization search


vector of axis label locations


Ported from Wilkinson's Java implementation with some changes. Changes: 1) m (the target number of ticks) is hard coded in Wilkinson's implementation as 5. Here we allow it to vary as a parameter. Since m is fixed, Wilkinson only searches over a fixed range 4-13 of possible resulting ticks. We broadened the search range to max(floor(m/2),2) to ceiling(6*m), which is a larger range than Wilkinson considers for 5 and allows us to vary m, including using non-integer values of m. 2) Wilkinson's implementation assumes that the scores are non-negative. But, his revised granularity function can be extremely negative. We tweaked the code to allow negative scores. We found that this produced better labelings. 3) We added 10 to Q. This seemed to be necessary to get steps of size 1. It is possible for this algorithm to find no solution. In Wilkinson's implementation, instead of failing, he returns the non-nice labels spaced evenly from min to max. We want to detect this case, so we return NULL. If this happens, the search range, mrange, needs to be increased.


Justin Talbot justintalbot@gmail.com


Wilkinson, L. (2005) The Grammar of Graphics, Springer-Verlag New York, Inc.

labeling documentation built on Aug. 30, 2023, 1:07 a.m.