Trouble with Axis Ticks

[Lorenzo Isella]

Dear All,
Please find an easy snippet at the end of the email.
I am reusing some old code of mine and I noticed that now (on a fresh
ggplot2 installation from the R repositories on a box running Debian
mint), I am experiencing troubles.
When I run my snippet, I get this error message

source('test_ggplot2.R')
Error in structure(list(...), class = "options") :
could not find function "unit"

The problem is given by the line

axis.ticks.length = unit(0.15, "cm")

inside ops(...). However, in the past on another machine, I have never got
any error message for this.
Is my new ggplot2 installation buggy or has anything changed recently in
its syntax?
In that case, what is the correct syntax now?
Many thanks for your help.
Cheers

Lorenzo


#################################################################

library(ggplot2)

mydata <- as.data.frame(cbind(seq(10), seq(10)))


names(mydata) <- c("ratio", "N")

b <- ggplot(mydata, aes(x=N, y=ratio)) +

geom_point(size=2) +

opts( panel.background=theme_rect(fill='white',
size=1.5))+
opts(panel.grid.minor = theme_blank())+
opts(panel.grid.major = theme_blank())+
opts(axis.ticks = theme_segment(colour = "black", size=1)
, axis.ticks.length = unit(0.15, "cm")
)

pdf("test.pdf",width=5,height=5)

print(b)
dev.off()

[Brandon Hurr]

Add, library(grid)

unit() is part of that package. I'm surprised by this. I know ggplot2 has stripped things away, but I didn't realize that it was quite this stripped down. 

[Dennis Murphy]

I believe this has to do with ggplot2 not autoloading packages at
startup as of 0.9.0. Just as you now have to explicitly load plyr and
reshape if you want to use them in a session, so too do you have to
load grid. Every once in a while you forget and get nipped...

Dennis