format secondary axis for dates
On Nov 16, 2010, at 2:32 PM, Jannis wrote:
Dear List, this may be a Newbi question and may have been asked several times, but i am too stupid to find the posts. I have a plot of values against POSIXct time steps. If I want to add a second x axis to the top margin of the plot, only numbers are at the tickmarks. Is there a straightforward way to specify the format to convert them to character representations (similar to the labels at the bottom)? x<-as.POSIXct(1:1000*(60^2),origin='01-01-1970')
The origin argument was incorrect and you got the wrong starting point: > x[1] [1] "0001-01-19 01:00:00 EST"
y=rnorm(1000) plot(x,y) axis(3)
This gives ticks at hourly intervals: axis(3, labels=format(x, "%Y-%m-%d"), at=x) Whereas this is probably what you want (after correcting the origin to "1970-01-01" axis.POSIXct(3, x=x, labels=TRUE )
David. > > > Thanks for your help > Jannis > > > > > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. David Winsemius, MD West Hartford, CT