| # File src/library/stats/R/relevel.R |
| # Part of the R package, https://www.R-project.org |
| # |
| # Copyright (C) 1995-2017 The R Core Team |
| # |
| # This program is free software; you can redistribute it and/or modify |
| # it under the terms of the GNU General Public License as published by |
| # the Free Software Foundation; either version 2 of the License, or |
| # (at your option) any later version. |
| # |
| # This program is distributed in the hope that it will be useful, |
| # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| # GNU General Public License for more details. |
| # |
| # A copy of the GNU General Public License is available at |
| # https://www.R-project.org/Licenses/ |
| |
| relevel <- function(x, ref, ...) UseMethod("relevel") |
| |
| relevel.default <- function(x, ref, ...) |
| stop("'relevel' only for (unordered) factors") |
| |
| relevel.ordered <- function(x, ref, ...) |
| stop("'relevel' only for unordered factors") |
| |
| relevel.factor <- function(x, ref, ...) |
| { |
| lev <- levels(x) |
| if(length(ref) != 1L) |
| stop("'ref' must be of length one") |
| if(is.character(ref)) |
| ref <- match(ref, lev) |
| if(is.na(ref)) |
| stop("'ref' must be an existing level") |
| nlev <- length(lev) |
| if(ref < 1 || ref > nlev) |
| stop(gettextf("ref = %d must be in 1L:%d", ref, nlev), domain = NA) |
| factor(x, levels = lev[c(ref, seq_along(lev)[-ref])]) |
| } |