総称関数

総称関数で，たとえば print は以下のように多数ある．

> methods(print)
  [1] print.acf*
  [2] print.anova
  [3] print.aov*

アスタリスクが付いているメソッドは，関数を直接確認できないことがある．namespase が分かれば :: を使って

> TukeyHSD
function (x, which, ordered = FALSE, conf.level = 0.95, ...)
UseMethod("TukeyHSD")
<bytecode: 0x24d9e08>
<environment: namespace:stats>
> stats::TukeyHSD
function (x, which, ordered = FALSE, conf.level = 0.95, ...)
UseMethod("TukeyHSD")
<bytecode: 0x24d9e08>
<environment: namespace:stats>

::: を使うと，関数本体を確認できる

> stats:::print.TukeyHSD
function (x, digits = getOption("digits"), ...)
{
    cat("  Tukey multiple comparisons of means\n")
    cat("    ", format(100 * attr(x, "conf.level"), 2), 
                   "% family-wise confidence level\n",
        sep = "")
    if (attr(x, "ordered"))
        cat("    factor levels have been ordered\n")
    cat("\nFit: ", deparse(attr(x, "orig.call"), 500), "\n\n",
        sep = "")
    xx <- unclass(x)
    attr(xx, "orig.call") <- attr(xx, "conf.level") <- attr(xx,
        "ordered") <- NULL
    xx[] <- lapply(xx, function(z, digits) {
        z[, "p adj"] <- round(z[, "p adj"], digits)
        z
    }, digits = digits)
    print.default(xx, digits, ...)
    invisible(x)
}
<bytecode: 0x2700660>
<environment: namespace:stats>

最初から

getS3method (f = "print", class = "TukeyHSD")

とする方法もあります．