>
> Well, when the error message says "argument 'lx' is missing, with no
> default", it really means that argument 'lx' is missing, with no
> default. Your panel function has an argument 'lx', which you forgot to
> change to 'ly' as you did with the prepanel function.
>
> Hope that helps...
>
> Thanks for the help Felix! It was a bit obvious what the problem was and I
apologize for not thinking about the error message more clearly.  I am going
to continue this as I think that it would be helpful if there was a working
example of this type of plot. Unfortunately, I do not have it yet. The
modified example below produced a stacked barplot with lovely error bars.
However, I can't seem to produce a plot that doesn't stack the bars.
stack=FALSE doesn't seem to have any effect. Any thoughts?

Thanks in advance.
Sam

#Generating the data
library(lattice)

temp <- abs(rnorm(81*5))
err <- as.data.frame(temp)
err$section=c("down","down","down","mid","mid","mid", "up","up", "up")

err$depth=c("Surface","D50", "2xD50")

err$err.date=c("05/09/2009","12/09/2009","13/10/2009","19/10/2009","21/09/2009")


err.split <-
     with(err,
          split(temp, list(depth,section, err.date)))

#I've tried to alter the panel function according to the thread to produce
#vertical error bars in my barcharts

prepanel.ci <- function(x, y, ly, uy, subscripts, ...) {

        y <- as.numeric(y)
        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 = 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.barchart(x, y, pch = pch, ...)
     }

se <-function(x) sqrt(var(x)/length(x))



err.ucl <- sapply(err.split,
            function(x) {
                st <- boxplot.stats(x)
                c(mean(x), mean(x) + se(x), mean(x) -se(x))
            })



err.ucl <- as.data.frame(t(err.ucl))
names(err.ucl) <- c("mean", "upper.se", "lower.se")
err.ucl$label <- factor(rownames(err.ucl),levels = rownames(err.ucl))

# add factor, grouping and by variables
err.ucl$section=c("down","down","down","mid","mid","mid", "up","up", "up")
err.ucl$depth=c("Surface","D50", "2xD50")

s
err.ucl$err.date=c("05/09/2009","12/09/2009","13/10/2009","19/10/2009","21/09/2009")

#This produces the figure I am looking for minus the error bars.

with(err.ucl, barchart(mean ~ err.date | section, group=depth,
        layout=c(1,3),
         horizontal=FALSE,
         scales=list(x=list(rot=45)),
        ))



#OK, now that this work and the error bars are drawn, I am curious why the
stack=TRUE doesn't produce each bar beside each other.

with(err.ucl, barchart(mean ~ err.date| section, group=depth,
         layout=c(1,3),
         horizontal=FALSE,
         stack=FALSE,
         scales=list(x=list(rot=45)),
         ly=lower.se,
         uy=upper.se,
         auto.key = list(points = FALSE, rectangles = TRUE, space= "right",
title = "Depth", border = TRUE),
         #auto.key=TRUE,
         prepanel=prepanel.ci,
         panel=panel.superpose,
         panel.groups=panel.ci
         ))



-- 
*****************************************************
Sam Albers
Geography Program
University of Northern British Columbia
3333 University Way
Prince George, British Columbia
Canada, V2N 4Z9
phone: 250 960-6777
*****************************************************

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