Contour Plot for Response Surface Fit
DESCRIPTION:
Makes a contour plot based on a response surface fit.
USAGE: 
contour.rsm.lm(rsm.object, vary, granularity = 50, ... )
REQUIRED ARGUMENTS:
rsm.object:
the output from fitting a response surface using rsm.lm.
OPTIONAL ARGUMENTS:
vary:
a list, with components named by the factors in rsm.object, that determines which two factors are varied on the x and y axes while the remaining factors are held constant. The components corresponding to the factors to be varied are assigned the value "v", while the remaining components are assigned either an explicit numeric value or the value "c" to indicate that the factor is to be held constant at its center point. (If a variable is omitted from the list, "c" is assumed.) By default, the first two factors in rsm.object are varied.
granularity:
integer length of the vectors containing the x and y coordinates of the grid over which the response is evaluated.
...:
other arguments passed to contour.default.
SIDE EFFECTS:
A contour plot is drawn on the current device.
DETAILS:
This function is a method for the generic function contour for class "rsm.lm". It can be invoked by calling contour for an object of the appropriate class, or directly by calling contour.rsm.lm regardless of the class of the object.
SEE ALSO:
contour , optim.rsm.lm , rsm.lm , rsm.design , surface.rsm.lm .
EXAMPLES: 
ab.rsm <- rsm.lm(abrsm.df)
contour(ab.rsm)


sda.od.rsm <- rsm.lm(sda.df)
contour(sda.od.rsm, levels = c(20,30,40,50,60),
        vary = list(Hinc.II = 'v', time = 'v'))
contour(sda.od.rsm, vary = list(Hinc.II = 'v',
        Exo.Klenow = 'v', time = 3))