R help - Jul 2008 - ggplot2: scaling and tick mark of x-axis

Dear list, 

i am trying to plot data in a way like this:

Date<-seq(as.Date("2006-08-29"), as.Date("2007-08-28"),
by="2 weeks")
var<-rnorm(27, 10000, 2500)
err<-rnorm(27, 3000, 1000)
df<-data.frame(cbind(Date, var, err))

library(ggplot2)

g <- ggplot(df, aes(x=Date, y=var, 
min=(var - err), max=(var + err)))

g1 <- g + geom_line() + geom_point() + geom_errorbar(width=2, linetype=1)

g2<-g1+scale_x_date(format="%d.%b.%Y")

It works, however i am not satisfied with the output. I would like to have 
the x-axis starting at "2006-08-01" and ending at
"2007-08-31" with tick
marks and labels and each 1st of the months.

I managed to do this with a trellis plot by defining 

Start<-as.Date("2006-08-01") ##1. August 2006
End <-as.Date("2007-09-01") ##1. September 2007 
Period<-seq(Start, Ende, by="month")

and then using "Period" as argument in scales(at). 

How can I succeed in ggplot2?

Cheers,

Henning



    
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Hi Henning,
> It works, however i am not satisfied with the output. I would like to have
> the x-axis starting at "2006-08-01" and ending at
"2007-08-31" with tick
> marks and labels and each 1st of the months.
Unfortunately this is a deficiency in the date scale - there's no way
to manually set the breaks.  It's on my to do list to fix, but I'm
currently working on some bigger things like a decent
theming/customisation system and a rewrite of the faceting code so it
may be a while before I get to it.  Currently, your only option is to
do something like this:

g <- ggplot(df, aes(as.numeric(Date), var, min=(var - err), max=(var + err)))
...
g + scale_x_continuous(breaks = as.numeric(Period), labels = Period)

Does that help?

Regards,

Hadley

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