posthocTGH function accepts formula.

R/posthocTGH.R

@@ -3,8 +3,28 @@
 #' This function is used by the 'oneway' function for oneway analysis of
 #' variance in case a user requests post-hoc tests using the Tukey or
 #' Games-Howell methods.
+#'
+#' @author Gjalt-Jorn Peters (Open University of the Netherlands) & Jeff Bagget
+#' (University of Wisconsin - La Crosse)
 #' 
+#' Maintainer: Gjalt-Jorn Peters <gjalt-jorn@@userfriendlyscience.com>
+#' @keywords utilities
+#' @examples
 #' 
+#' ### Compute post-hoc statistics using the tukey method
+#' posthocTGH(y=ChickWeight$weight, x=ChickWeight$Diet, method="tukey");
+#' posthocTGH(weight ~ Diet, data = ChickWeight, method="tukey");
+#' ### Compute post-hoc statistics using the games-howell method
+#' posthocTGH(y=ChickWeight$weight, x=ChickWeight$Diet);
+#' posthocTGH(weight ~ Diet, data = ChickWeight);
+#'
+#' @export posthocTGH
+posthocTGH <- function(...) {
+    UseMethod("posthocTGH")
+}
+
+#' @rdname posthocTGH
+#'
 #' @param y y has to be a numeric vector.
 #' @param x x has to be vector that either is a factor or can be converted into
 #' one.
@@ -37,22 +57,10 @@
 #' \code{userfriendlyscience} version 0.6-2, the default of this setting
 #' changed from \code{"holm"} to \code{"none"} (also see
 #' https://stats.stackexchange.com/questions/83941/games-howell-post-hoc-test-in-r).
-#' @author Gjalt-Jorn Peters (Open University of the Netherlands) & Jeff Bagget
-#' (University of Wisconsin - La Crosse)
-#' 
-#' Maintainer: Gjalt-Jorn Peters <gjalt-jorn@@userfriendlyscience.com>
-#' @keywords utilities
-#' @examples
-#' 
-#' ### Compute post-hoc statistics using the tukey method
-#' posthocTGH(y=ChickWeight$weight, x=ChickWeight$Diet, method="tukey");
-#' ### Compute post-hoc statistics using the games-howell method
-#' posthocTGH(y=ChickWeight$weight, x=ChickWeight$Diet);
-#' 
-#' @export posthocTGH
-posthocTGH <- function(y, x, method=c("games-howell", "tukey"),
-                       conf.level = 0.95, digits=2,
-                       p.adjust="none", formatPvalue = TRUE) {
+#'
+posthocTGH.default <- function(y, x, method=c("games-howell", "tukey"),
+                               conf.level = 0.95, digits=2,
+                               p.adjust="none", formatPvalue = TRUE) {
   ### Based on http://www.psych.yorku.ca/cribbie/6130/games_howell.R
   method <- tolower(method);
   tryCatch(method <- match.arg(method), error=function(err) {
@@ -167,6 +175,37 @@ posthocTGH <- function(y, x, method=c("games-howell", "tukey"),
 
 }
 
+#' @rdname posthocTGH
+#'
+#' @param formula A formula specifying the model.
+#' @param data an optional matrix or data frame (or similar: see
+#' \code{\link{model.frame}}) containing the variables in the formula
+#' \code{formula}.  By default the variables are taken from
+#' \code{environment(formula)}.
+#' @param subset an optional vector specifying a subset of observations
+#' to be used.
+#' @param na.action a function which indicates what should happen when the data
+#' contain \code{NA}s. Defaults to \code{getOption("na.action")}.
+#' @param \dots further arguments to be passed to or from methods.
+#'
+posthocTGH.formula <- function(formula, data, subset, na.action, ...)
+{
+    if(missing(formula)
+       || (length(formula) != 3L)
+       || (length(attr(terms(formula[-2L]), "term.labels")) != 1L))
+        stop("'formula' missing or incorrect")
+    m <- match.call(expand.dots = FALSE)
+    if(is.matrix(eval(m$data, parent.frame())))
+        m$data <- as.data.frame(data)
+    ## need stats:: for non-standard evaluation
+    m[[1L]] <- quote(stats::model.frame)
+    m$... <- NULL
+    mf <- eval(m, parent.frame())
+    DATA <- list(mf[,1], mf[,2])
+    y <- do.call("posthocTGH", c(DATA, list(...)))
+    y
+}
+
 print.posthocTGH <- function(x, digits=x$input$digits, ...) {
   print(x$intermediate$descriptives, digits=digits);
   cat('\n');