From Augix' Wiki

Description

Performs one and two sample Wilcoxon tests on vectors of data for possibly tied observations. Compare to normal wilcox.test, it can deal with the tie problem.

Package

It's in the package exactRankTests.

Usage

     ## Default S3 method:
     wilcox.exact(x, y = NULL, alternative = c("two.sided", "less", "greater"),
                  mu = 0, paired = FALSE, exact = NULL,  
                  conf.int = FALSE, conf.level = 0.95, ...)
     ## S3 method for class 'formula':
     wilcox.exact(formula, data, subset, na.action, ...)