[R] ggplot2 date help (minor gridlines months and major grid lines years in a readable format)

[stephen sefick]

library(ggplot2)

melt.updn <- (structure(list(date = structure(c(11808, 11869, 11961, 11992,
12084, 12173, 12265, 12418, 12600, 12631, 12753, 12996, 13057,
13149, 11808, 11869, 11961, 11992, 12084, 12173, 12265, 12418,
12600, 12631, 12753, 12996, 13057, 13149), class = "Date"), variable =
structure(c(1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("unrestored",
"restored"), class = "factor"), value = c(1.1080259671261, 0.732188576856918,
0.410334408061265, 0.458980396410056, 0.429867902470711, 0.83126337241925,
0.602008712602784, 0.818751283264408, 1.12606382402475, 0.246174719479079,
0.941043753226865, 0.986511619794787, 0.291074883642735, 0.346361775752625,
1.36209038621623, 0.878561166753624, 0.525156715576168, 0.80305564765846,
1.08084449441812, 1.24906568558731, 0.970954515841768, 0.936838439269239,
1.26970090246036, 0.337831520417547, 0.909204325710795, 0.951009811036613,
0.290735620653709, 0.426683515714219)), .Names = c("date", "variable",
"value"), row.names = c(NA, -28L), class = "data.frame"))

qplot(date, value, data=melt.updn, shape=variable, ylab="Distance"
,main="Euclidean Distances Time
Series")+geom_line()+theme_bw()+geom_vline(x=as.numeric(as.Date("2002-11-01")))

# I would like to add minor grid lines so that months of the year can
be distinguished.
# even tick marks would be acceptable.  I have tried to wade through
the book on Hadley's site and I can not figure this one out

thanks for the help,

-- 
Stephen Sefick

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

								-K. Mullis