[R] plotting step functions in plot vs. xyplot

Dylan Beaudette dylan.beaudette at gmail.com
Mon Dec 3 01:29:37 CET 2007


I have noticed an odd inconsistency when plotting a 'step' function
(type='s') in xyplot() vs. plot().

For example, given the following data:

## generate some profile depths: 0 - 150, in 10 cm increments
depth <- seq(0,150, by=10)
## generate some property: random numbers in this case
prop <- rnorm(n=length(depth), mean=15, sd=2)
## since the 0 is not a depth, and we would like the graph to start from 0
## make the first property row (associated with depth 0) the same as the second
## property row
prop[1] <- prop[2]
## combine into a table: data read in from a spread sheet would
already be in this format
soil <- data.frame(depth=depth, prop=prop)

## simple depth plot, as steps: looks good!
plot(depth ~ prop, data=soil, ylim=c(150,0), type='s', ylab='Depth',
xlab='Property', main='Property vs. Depth Plot')

## now try it with lattice graphics:yuck!
xyplot(depth ~ prop, data=soil, ylim=c(160,-5), type='s',
ylab='Depth', xlab='Property', main='Property vs. Depth Plot')

it looks like the data isn't rotated (?) correctly - i.e. the axis and
data do not match.

Now, am I mis-interpreting the meaning of type='s' in lattice graphics?

here is my R session info:
R version 2.4.1 (2006-12-18)


attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"  "methods"
[7] "base"

other attached packages:

could it be that my version of R and lattice is just too old?

thanks in advance!


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