[R] Plotting times at night and getting plot limits correct

[Richard M. Heiberger]

Try this.

>From the full data-time value subtract 18:00:00.
This places the times you are interested in into the range 00:00:00 - 12:00:00
Remove the date from these adjusted date-time values and plot y
against the new times.
Take control of the tick-labels and display 18:00 - 0600 instead of
the default 00:00 - 12:00

Rich

On Tue, May 12, 2015 at 10:34 AM, Bob O'Hara <rni.boh at gmail.com> wrote:
> I'm helping colleagues with analysis of frog calls at night, and they
> want to plot call statistics against time. This means we hit a
> problem: we want the x-axis to start at (say) 18:00 and end at (say)
> 06:00. I'm reluctant to use the date as well, because we have data
> from several dates, but only want to plot against time of day.
>
> Here's some code to illustrate the problem (don't worry about the data
> being outside the range of the plot: this is only for illustration).
>
> library(chron)
> Times <- chron(times.=paste(c(18:23,0:9),":30:00", sep=""))
> Thing <- rnorm(length(Times)) # just something for the y-axis
>
> plot(Times,Thing) # x-axis wrong
> plot(Times,Thing, xlim=chron(times.=c("05:00:00", "18:00:00"))) # x-axis right
> plot(Times,Thing, xlim=chron(times.=c("18:00:00", "05:00:00"))) #
> would like this to work...
>
> Can anyone suggest a solution?
>
> Bob
>
> --
> Bob O'Hara
>
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