[R] how do I eliminate excess levels in lattice contourplot key / legend?

Seth W Bigelow sbigelow at fs.fed.us
Wed Dec 3 18:13:57 CET 2008

I'm working on a contourplot( ) graph, the subject of several previous 
posts to this list. The contours express probabilities from 0 - 1, but the 
key that is automatically generated by contourplot pads the probability 
scale with values that are impossible (i.e, range goes from -0.2 to 1.2), 
which will be confusing to those who view the plot. How can I get the 
scale to just run from 0 - 1?

I have toiled mightily in the depths of the Murrell & Sarkar graphics 
books. Any pointers will be gratefully received.


Minimal, commented code:


model <- function(a,b,c,d,e, f, X1,X2)          # model function for 
contour plot
{J <- a + (b*X1) + (c*X2) + (d*X1*X2) + e*(X1^2) + f*(X2^2)
  pp <- exp(J)/(1+exp(J))

g <- expand.grid(X1= seq(0.3,0.9,0.01), X2 = seq(0.3,1, 0.01)) 
## create x and y data matrix

g$z <- model(-29, -14, 52, 80, -3, -56, g$X1, g$X2) 
## Create variable z using model and g data frame

contourplot(z ~ X1 * X2,
data = g,
region = TRUE,         # Add color to background
cuts = 5            # Number of contour/color intervals. 

Dr. Seth  W. Bigelow
Sierra Nevada Research Center

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