[R] Plotting Time against Date for time series data?

[Sander Oom]

The plot is nearly there! Using the axis.POSIXct command I have got the 
x-axis under control. However, the units for the y-axis (Time) are in 
seconds by default (i.e. range is from 0 to 1440). I'm trying to plot hours 
along the y-axis, without changing the units for the plot itself, but 
without any luck.

The #'s were a quick solution to stop WinEdt reformatting my code 
automatically, now I discovered I can switch to a different wrap mode.

This is the code just now:

 >
 > psDateTime <- function(DateTime, FileName){
+     strFileName <- paste("Analysis\\Graphics\\time_date_", FileName, sep 
= "")
+     startMonth <- as.POSIXct(as.Date("01/09/2003", format="%d/%m/%Y"))
+     endMonth <- as.POSIXct(as.Date("01/06/2004", format="%d/%m/%Y"))
+     startTime <- as.POSIXct(as.Date("00:00:00", format="%H:%m:%s"))
+     endTime <- as.POSIXct(as.Date("23:59:59", format="%H:%m:%s"))
+     Date <- trunc(DateTime, "day")
+     Time <- DateTime - Date
+     postscript(strFileName)
+     plot(x=Date, y=Time,
+         xlab= "Date (month/year)", ylab= "Time (hours)", xaxt="n", #yaxt="n",
+         xlim=c(as.POSIXct(startMonth), as.POSIXct(endMonth)),
+         ylim=c(as.POSIXct(startTime), as.POSIXct(endTime))
+         )
+     axis.POSIXct(1, at=seq(startMonth, endMonth, by="month"), format="%m/%y")
+     axis.POSIXct(2, at=seq(startTime, endTime, by="hours"), format="%H")
+     pstamp(pwd=FALSE, time=TRUE)
+     dev.off()
+ }
 > psDateTime(datKruger1$DaTim, "datKruger1.eps")
Error in plot.window(xlim, ylim, log, asp, ...) :
         need finite ylim values
 >

and when removing the ylim line from the above code, an error associated 
with the 'axis.POSICct(2....)' line:

 > psDateTime(datKruger1$DaTim, "datKruger1.eps")
Error in if (to <= from) stop("`to' must be later than `from'") :
         missing value where TRUE/FALSE needed
 >

Any help much appreciated,

Sander.

At 15:58 2004/05/17, you wrote:
>On Mon, 17 May 2004, Slist wrote:
>
> > I have a data set containing GPS fixes of animal locations. To check that
> > the GPS's are working properly, I would like to plot the time of the fixes
> > (y-axis) against the date of the fixes (x-axis). If all works well, the
> > plot should show four regular fixes per day. The x-axis should be labelled
> > with month/year (i.e. 11/04) and the y-axis by hour from 00 to 24. I would
> > like to control the x-axis limits.
> >
> > I have looked at several date and time related help pages, but get 
> horribly
> > lost in all the terminology. The main challenge is to isolate date and 
> time
> > from the date/time object for plotting (marked ???). Therefore, I would
> > like the following example code to work:
> >
> >  >
> >  >
> > dates <- c("02/27/92", "02/27/92", "01/14/92", "01/14/92", "03/28/92", 
> "03/28/92") #
> > times <- c("23:03:20", "10:29:56", "01:03:30", "13:03:30", "18:21:03", 
> "06:56:26") #
> > x <- paste(dates, times) #
> > DateTime <- strptime(x, "%m/%d/%y %H:%M:%S") #
>
>Why do you end lines with #?  It is rather confusing.
>
>Date <- trunc(DateTime, "day")
>Time <- DateTime - Date
>plot(Date, Time)
>
>appears to do what you want (except the x axis labelling, which you can
>alter by a call to axis.POSIXct and x-axis limits, which need to be set
>via xlim as a POSIXct object.).
>
>--
>Brian D. Ripley,                  ripley at stats.ox.ac.uk
>Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>University of Oxford,             Tel:  +44 1865 272861 (self)
>1 South Parks Road,                     +44 1865 272866 (PA)
>Oxford OX1 3TG, UK                Fax:  +44 1865 272595