CODEWITHSUNDEEP
rbar-chartlattice
Pieter
Pieter

Reputation: 3399

add labels to lattice barchart

I would like to place the value for each bar in barchart (lattice) at the top of each bar. However, I cannot find any option with which I can achieve this. I can only find options for the axis.

Upvotes: 10

Views: 6813

Answers (4)

rcs
rcs

Reputation: 68849

Create a custom panel function, e.g.

library("lattice")
p <- barchart((1:10)^2~1:10, horiz=FALSE, ylim=c(0,120),
              panel=function(...) { 
                args <- list(...)
                panel.text(args$x, args$y, args$y, pos=3, offset=1)
                panel.barchart(...)
              })
print(p)

lattice barchart with labels

Upvotes: 21

Dav Clark
Dav Clark

Reputation: 1460

Since I had to do this anyway, here's a close-enough-to-figure it out code sample along the lines of what @Alex Brown suggests (scores is a 2D array of some sort, which'll get turned into a grouped vector):

barchart(scores, horizontal=FALSE, stack=FALSE, 
     xlab='Sample', ylab='Mean Score (max of 9)',
     auto.key=list(rectangles=TRUE, points=FALSE),
     panel=function(x, y, box.ratio, groups, errbars, ...) {
         # We need to specify groups because it's not actually the 4th 
         # parameter
         panel.barchart(x, y, box.ratio, groups=groups, ...)
         x <- as.numeric(x)
         nvals <- nlevels(groups)
         groups <- as.numeric(groups)
         box.width <- box.ratio / (1 + box.ratio)
         for(i in unique(x)) {
             ok <- x == i
             width <- box.width / nvals
             locs <- i + width * (groups[ok] - (nvals + 1)/2)
             panel.arrows(locs, y[ok] + 0.5, scores.ses[,i], ...)
         }
     } )

I haven't tested this, but the important bits (the parts determining the locs etc. within the panel function) do work. That's the hard part to figure out. In my case, I was actually using panel.arrows to make errorbars (the horror!). But scores.ses is meant to be an array of the same dimension as scores.

I'll try to clean this up later - but if someone else wants to, I'm happy for it!

Upvotes: 0

Alex Brown
Alex Brown

Reputation: 42902

If you are using the groups parameter you will find the labels in @rcs's code all land on top of each other. This can be fixed by extending panel.text to work like panel.barchart, which is easy enough if you know R.

I can't post the code of the fix here for licencing reasons, sorry.

Upvotes: -1

Shane
Shane

Reputation: 100194

I would have suggested using the new directlabels package, which can be used with both lattice and ggplot (and makes life very easy for these labeling problems), but unfortunately it doesn't work with barcharts.

Upvotes: 0

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