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
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David Winsemius, MD
West Hartford, CT
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