Summary Plots by Factors
DESCRIPTION:
Produces plots, such as side by side boxplots, based on each level of the factor.
USAGE: 
plot.factor(x, y=NULL, style="box", rotate=<<see below>>,
   boxmeans=F, character=<<see below>>, data=NULL)
REQUIRED ARGUMENTS:
x:
either a factor, a design or data frame, or a formula. If a formula, the response must be present in the formula.
OPTIONAL ARGUMENTS:
y:
the response vector, if x is a factor, or x is a design or data frame not containing the response (in which case this argument is required). If x is a formula, then a design or data frame may be given here. Or x can be the data frame and y the formula.
style=:
character string indicating style of plot. Possible values are "box" (default), "fraction non0", "shaded bar", and "character". The names can be abbreviated (one character is enough). The four styles produce: box-plots; bar-plots of the fraction of observations not equal to 0; shaded bars with each shaded area representing the number of observations having a particular value; characters plotted at the values of y, the characters given by argument character=. Supplying argument character= implies the style.
rotate=:
if TRUE, x-axis labels will be rotated. The default is sum(nchar(xalabs))>80.
boxmeans=:
TRUE if you want the mean of the boxplots to be indicated. Applicable for style="box" only.
character=:
name of factor whose levels will be used as plotting characters.
data=:
a data frame containing the data if x was given as a formula.

Graphical parameters may also be supplied as arguments to this function (see par).

SIDE EFFECTS:
produces a set of plots, one for each factor. Levels of the factor are arranged along the x-axis. Depending on the value of style, a box, bar, shaded bar, or characters will be plotted at each level.
DETAILS:
This function is a method for the generic function plot for class "factor". It can be invoked by calling plot for an object of the appropriate class, or directly by calling plot.factor regardless of the class of the object.
REFERENCES:
A. E. Freeny and J. M. Landwehr (1990), Displays for data from large designed experiments, Computer Science and Statistics: Proceedings of the 22nd Symposium on the Interface. pp 117-126, Springer Verlag.
SEE ALSO:
plot , plot.design , factor .
EXAMPLES: 
# do box plots of all factors.
plot.factor(catalyst, Yield ~ ., character = catalyst$Temp,
        main = "Yield, points identified by levels of Temp")


plot.factor(skips ~ Opening + Mask, solder.balance)
plot.factor(skips ~ Opening + Mask, data=solder.balance)


# do character plot of interaction
attach(solder.balance)
Boards <- interaction(Solder, Mask, Opening)
plot.factor(Boards, skips, character = Panel, rotate = T)


plot.factor(skips ~ Opening + Mask)