wilcox.test(x, ...)
## Default S3 method:
wilcox.test(x, y = NULL,
alternative = c("two.sided", "less", "greater"),
mu = 0, paired = FALSE, exact = NULL, correct = TRUE,
conf.int = FALSE, conf.level = 0.95, ...)
#ex. with mtcars
wilcox.test(mpg ~ am, data=mtcars)