add basic plot(<factor>) example

git-svn-id: https://svn.r-project.org/R/trunk@87423 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: smeyer

src/library/graphics/man/plot.factor.Rd

@@ -1,14 +1,14 @@
 % File src/library/graphics/man/plotfactor.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2009 R Core Team
+% Copyright 1995-2024 R Core Team
 % Distributed under GPL 2 or later
 
 \name{plot.factor}
+\alias{plot.factor}
 \title{Plotting Factor Variables}
 \usage{
-\method{plot}{factor}(x, y, legend.text = NULL, \dots)
+\method{plot}{factor}(x, y, legend.text = NULL, ...)
 }
-\alias{plot.factor}
 \arguments{
     \item{x, y}{numeric or factor. \code{y} may be missing.}
     \item{legend.text}{character vector for annotation of y axis in the
@@ -17,18 +17,18 @@
     \item{\dots}{Further arguments to \code{\link{barplot}},
       \code{\link{boxplot}}, \code{\link{spineplot}} or
       \code{\link{plot}} as appropriate.  All of these accept
-      \link{graphical parameters} (see \code{\link{par}}) and
+      \link{graphical parameters} (see \code{\link{par}}),
       annotation arguments passed
-      to \code{\link{title}} and \code{axes = FALSE}.  None accept \code{type}.
+      to \code{\link{title}}, and \code{axes = FALSE}.  None accept \code{type}.
     }
 }
 \description{
   This method is used for
   \code{\link{factor}} arguments of the \emph{generic}
   \code{\link{plot}} function,
-  possibly called from the formula method (see the Examples).
+  possibly called from the formula method.
 
-  If \code{y} is missing \code{\link{barplot}} is produced.
+  If \code{y} is missing a \code{\link{barplot}} is produced.
   For numeric \code{y} a \code{\link{boxplot}} is used, and for a factor
   \code{y} a \code{\link{spineplot}} is shown.  For any other type of
   \code{y} the next \code{plot} method is called, normally
@@ -40,9 +40,12 @@
 }
 \examples{
 require(grDevices)
-% this does not call plot.factor!
-% plot(PlantGrowth)                                # -> plot.data.frame
-plot(weight ~ group, data = PlantGrowth)           # numeric vector ~ factor
+
+plot(state.region)
+
+## called from the formula method
+plot(~ group, data = PlantGrowth)
+plot(weight ~ group, data = PlantGrowth)           # numeric ~ factor
 plot(cut(weight, 2) ~ group, data = PlantGrowth)   # factor ~ factor
 ## passing "..." to spineplot() eventually:
 plot(cut(weight, 3) ~ group, data = PlantGrowth,

tests/Examples/graphics-Ex.Rout.save

@@ -2174,7 +2174,12 @@ Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’
 > ### ** Examples
 > 
 > require(grDevices)
-> plot(weight ~ group, data = PlantGrowth)           # numeric vector ~ factor
+> 
+> plot(state.region)
+> 
+> ## called from the formula method
+> plot(~ group, data = PlantGrowth)
+> plot(weight ~ group, data = PlantGrowth)           # numeric ~ factor
 > plot(cut(weight, 2) ~ group, data = PlantGrowth)   # factor ~ factor
 > ## passing "..." to spineplot() eventually:
 > plot(cut(weight, 3) ~ group, data = PlantGrowth,