[R] help with plotting error bars on xyplot!

[Paulo Pagliari]

Dear R helpers,

I am trying to create a xyplot similar to this one:

https://stat.ethz.ch/pipermail/r-help/2008-June/164968.html

I can plot the data correctly when I only have one Y. However, I need to add another Y (Y2) to the plot and each Y must have their own error bars and also different symbols.  You will see that in this plot symbol changes based on X and not Y. The symbols should change by Y category, for example in the example below, the symbols with the errors bars sould be one symbol while the symbols without errors bars should have a different symbol and also should have error bars. Any help will be much appreciated.



Hr = c(0,1,2,3,4,5,0,1,2,3,4,5)
DRUG = rep(c("D", "P"), each=6)
Y = c(1,2,2,2,2,1,3, 4, 4,4, 4, 3)
Y2 = c(2,3,3,3,3,2,4, 5, 5,5, 5, 4)
data = data.frame(Hr, DRUG, Y, Y2)
data$lower1 = data$Y - .5
data$upper1 = data$Y + .5
data$lower2 = data$Y2 - .5
data$upper2 = data$Y2 + .5


prepanel.ci <- function(x, y, ly, uy, subscripts, ...) {
    x <- as.numeric(x)
    ly <- as.numeric(ly[subscripts])
    uy <- as.numeric(uy[subscripts])
    list(ylim = range(y, uy, ly, finite = TRUE)) }

panel.ci <- function(x, y, ly, uy, subscripts, pch = c(1, 16), ...) {
    x <- as.numeric(x)
    y <- as.numeric(y)
    ly <- as.numeric(ly[subscripts])
    uy <- as.numeric(uy[subscripts])
     panel.arrows(x, ly, x, uy, col = "black",
                 length = 0.25, unit = "native",
                 angle = 90, code = 3)
    panel.xyplot(x, y, pch = c(1, 16), ...)}

xyplot(Y+Y2 ~ Hr,
        data=data, 
        ly = data$lower1,
        uy = data$upper1,
        prepanel = prepanel.ci,
        panel = panel.superpose,
        panel.groups = panel.ci,
        auto.key = list(space = "top",  text = c( "D","P"), points = FALSE,
lines = TRUE, columns=2))




Paulo H. Pagliari, PhD. 
Assistant Professor Extension Soil Scientist 
University of Minnesota 
Southwest Research and Outreach Center 
23669 130th St. 
Lamberton, MN 56152 
Tel. 507-752-5065 
FAX 507-752-5097
email: pagli005 at umn.edu




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