[R] Troubles with the format of dates

[Kathi]

Thank you _SO_ much, Petr, you helped me again. That worked like a charm, exactly what I needed! 

Cheers,
Kathi 

On Thu, 27 Nov 2008 15:01:29 +0100, Petr PIKAL wrote
> Hi
> 
> r-help-bounces at r-project.org napsal dne 27.11.2008 14:20:17:
> 
> > Dear useRs,
> > 
> > I'm struggling again with date-related stuff: I am using R to draw water
> 
> > levels at certain measuring 
> > stations. My data comes as a tab-delimited text file and looks like 
> this:
> > 
> > DATUM   P1   P2
> > ...
> > 2006-11-16       425.21   423.99 
> > 2006-12-15     425.12   423.97 
> > 2007-01-16       425.16   424.06 
> > ...
> > 
> > (measurements started in July 2004 and still continue on a monthly or 
> bi-weekly basis)
> > 
> > This is then plotted using this code:
> > 
> > a<-read.table("dummy_data.tab", sep="\t", header=TRUE, na.strings=c(0))
> > x<-as.Date(a$DATUM)
> > 
> > plot(x, a$P1, axes=FALSE, xlim=c(as.Date("2004-07-01"), 
> as.Date("2009-01-01")), 
> > ylim=c(423,428), col="red", pch=15, type="o", ylab="Kote [m a.s.l.]", 
> > main="Dummy Plot")
> > points(x, a$P2, col="red", pch=17, type="o", lty="dotted")
> > axis(2, at=423:428, tck=1, col="gray60")
> > axis.Date(1, at=seq(as.Date("2004-07-01"), as.Date("2009-01-01"), 
> > by="month"), labels=seq(as.Date("2004-07-01"), as.Date("2009-01-01"), 
> > by="month"), tck=1, col="gray60")
> > 
> > So far, I've been using this type of date format (yyyy-mm-dd) because 
> that was
> > the only way I could 
> > get  the whole thing to work when I started using R. However, living in 
> > Switzerland, I would prefer 
> > the dates to read 16.11.2006 i.e. dd.mm.yyyy or 16. Nov. 2006 
> (preferably 
> > using German names for 
> > the months, if possible). 
> > 
> > I've used the chron package to convert my dates to day mon year (16 Nov 
> 2006, 
> > with or without 
> > spaces), i.e. I replaced the second line of code with:
> > 
> > x<-format(chron(as.character(a$DATUM), format="y-m-d", out.format="day 
> mon year"))
> 
> Although I am not an expert in time/date functions it seems to me 
> that you just want your labels to be in your preferred format. If it 
> is the case
> 
> labels = format(seq(as.Date("2004-07-01"), as.Date("2009-01-01"), 
> by="month"), "%d.%m.%Y")
> 
> in your call to axisDate can help you to achieve it.
> 
> Regards
> Petr
> 
> > 
> > but then I can't plot them any more, because as.Date() no longer is the 
> > correct function and R gives 
> > me an error saying there is an invalid xlim-value. Can someone please 
> point me
> > in the right 
> > direction?
> > 
> > I could easily change the input data to be in dd.mm.yyyy format, if that 
> helps.
> > 
> > Thanks for your help,
> > 
> > Kathi
> > 
> > 
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