Add equalizeLevels to make 2 data.frames equal in its factors.

R/equalizeLevels.R

+#' @title Make that to data frames have the same factor levels
+#'
+#' @name equalizeLevels
+#'
+#' @description If two data frames have factor or character columns with
+#'     the same name, those in the first will have the same level order
+#'     as those in the second. So, in terms of factor columns, these
+#'     data frames will have the same levels in the same
+#'     order. Character columns in the first will be converted to factor
+#'     if they aren't. This function is useful to assing to the data
+#'     frame returned in the \code{grid} attribute returned by
+#'     \code{doBy::LSmeans()} or \code{doBy::LSmatrix()} the same order
+#'     to the levels present in the data frame used to fit the model and
+#'     estimate the parameters.
+#'
+#' @param \code{target} the target data frame that will have factor
+#'     levels reordered.
+#' @param \code{ref} the reference data frame that contains the desired
+#'     level order.
+#'
+#' @return the first data data frame with the levels in a new order.
+#'
+#' @seealso \link[doBy]{LSmeans}, \link[doBy]{LSmatrix}.
+#'
+#' @author Walmes Zeviani, \email{walmes@@ufpr.br}
+#'
+#' @export
+#'
+#' @examples
+#'
+#'
+equalizeLevels <- function(target, ref){
+    if(is.data.frame(target) & is.data.frame(ref)){
+        com <- intersect(names(target), names(ref))
+        for(i in com){
+            if(!is.null(levels(ref[,i]))){
+                target[,i] <- factor(target[,i], levels=levels(ref[,i]))
+            }
+        }
+        target
+    }
+    else stop("`target` and `ref` must be a data.frame.")
+}
+
+a <- data.frame(
+    Species=as.character(sample(iris$Species, size=10, replace=TRUE)),
+    stringsAsFactors=FALSE)
+str(a)
+
+levels(a$Species)
+levels(iris$Species)
+
+b <- equalizeLevels(target=a, ref=iris)
+str(b)