[R] image.plot adding x-axis labels. Please Help

[David Lyon]

if I had a data file like this:
1.42 1.29 -0.13
1.46 1.34 -0.12
1.45 1.32 -0.13
1.36 1.26 -0.10
1.33 1.29 -0.04

I want to create a image plot like this:
data1<-read.table("A")

image.plot(t(data1), axes=FALSE, xlab=NA, ylab=NA)

I cant get the labels for the x axis right can some kind person help me?
axis(1.....???????.....labels=c("A", "B", "C"))


Many thanks in advance!