Hi Seth,
An alternative would be to use ggplot2, http://had.co.nz/ggplot2:
model <- function(a,b,c,X1,X2) {
(exp(a + b*X1 + c*X2)) / (1 + exp(a + b*X1 + c*X2))
}
g <- expand.grid(X1 = seq(0.40, 0.8,0.01), X2 = seq(0.03,0.99,0.03))
a <- -37.61
b <- 34.88
c <- 28.44
g$z<- model(a, b, c, g$X1,g$X2)
ph <-c(0.42,0.47,0.59,0.40)
phh <-c(0.76,0.81,0.82,0.71)
d <- data.frame(ph,phh)
library(ggplot2)
qplot(X1, X2, data = g, fill = z, geom="tile", xlab="p(H)", ylab="p(H|H)")+
geom_contour(aes(z=z)) +
geom_point(aes(x = ph, y = phh, fill = NULL), data=d)
Plots in ggplot2 have multiple layers which can have different data sources.
Hadley
On 12/13/07, Seth W Bigelow <[EMAIL PROTECTED]> wrote:
>
> Friends: I wish to overlay data points on a contour graph. The following
> example produces a nice contour plot, but I have not mastered the concept
> of using panel functions to modify plots. Can someone show me how to
> overlay the data points (given after contour plot statement) on the
> contourplot?
> --Seth
>
>
> model <- function(a,b,c,X1,X2) # provide model
> function for contour plot
> {(exp(a + b*X1 + c*X2)) / (1 + exp(a + b*X1 + c*X2))}
>
> g <- expand.grid(X1 = seq(0.40, 0.8,0.01), X2 = seq(0.03,0.99,0.03)) #
> create gridded data for contour plot
> a <- -37.61 # Assign value to 'a' parameter
> b <- 34.88 # Assign value to 'b' parameter
> c <- 28.44 # Assign value to 'c' parameter
> g$z<- model(a, b, c, g$X1,g$X2) # Create variable z
> using gridded data, model, and variables
>
> contourplot(z ~ X1 * X2, # specify the basic
> equation for the contour plot
> data=g, # Specify the data frame to be
> used
> contour=TRUE, # Make sure it adds
> contours
> xlim=c(0.4,0.8), ylim=c(0.401,0.999), zlim=c(0,1), # Set axis
> ranges
> xlab="p(H)", ylab="p(H|H)", # Add axis labels
> region = TRUE, # Add nice colors
> cuts=10 # Specify number of contour
> slices
> )
>
> # Data to superimpose as xyplot on the contourplot....
>
> ph <-c(0.42,0.47,0.59,0.40) # Create a vector of values
> under variable 'ph'
> phh <-c(0.76,0.81,0.82,0.71) # Create vector of
> values for variable 'phh'
> d <- data.frame(ph,phh) # Group variables ph
> & phh in data frame 'd'
>
>
>
>
> Dr. Seth W. Bigelow
> Biologist, Sierra Nevada Research Center
> Pacific Southwest Research Station, USDA Forest Service
> Mailing address: 2121 2nd St Suite A101, Davis CA 95616
> www.fs.fed.us/psw/programs/snrc/staff/bigelow
> www.smbigelow.net
> Phone: 530 759 1718
> Fax: 530 747 0241
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
http://had.co.nz/
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
