[R] abline(v= x) in plot with time formated xaxis not working

[jim holtman]

The reason that you need the 'as.POSIXct' is that the 'abline'
function does not recognize variables with POSIXlt class.

> methods(abline)
no methods were found
Warning message:
In methods(abline) : function 'abline' appears not to be generic
> methods(plot)
 [1] plot.acf*           plot.data.frame*    plot.Date*
plot.decomposed.ts* plot.default
 [6] plot.dendrogram*    plot.density        plot.ecdf
plot.factor*        plot.formula*
[11] plot.hclust*        plot.histogram*     plot.HoltWinters*
plot.isoreg*        plot.lm
[16] plot.medpolish*     plot.mlm            plot.POSIXct*
plot.POSIXlt*       plot.ppr*
[21] plot.prcomp*        plot.princomp*      plot.profile.nls*
plot.sar            plot.spec
[26] plot.spec.coherency plot.spec.phase     plot.srx.file
plot.stepfun        plot.stl*
[31] plot.table*         plot.ts             plot.tskernel*
plot.TukeyHSD

'plot' knows how to handle POSIXct/lt classes.  You need to at least
convert to POSIXct since the value will be within the range of what
the x-axis is:

> str(event.1)
 POSIXlt[1:9], format: "2009-07-19 15:28:33"
> par('usr')
[1] 1248015314.4 1248023025.6         58.8       1036.2
> unclass(as.POSIXct(event.1))
[1] 1248017313
attr(,"tzone")
[1] "GMT"

This shows the extent of the x-axis and then what the value of event.1
will be after conversion to POSIXct.

HTH

On Sun, Jul 19, 2009 at 11:33 AM, F!!<pech at students.uni-mainz.de> wrote:
>
> Sorry for the lack of the plot. It's is just a simple xy plot with xvalues
> formated as shown in my post (strptime()).
>
> Anyway, here a working example:
>
>
>
>>
>> rm(list=ls())
>>
>> x<-c(100*1500:1559, 100*1600:1659)
>> x<-strptime(x, format="%H%M%S")
>> y<-c(CO2$conc, CO2$conc[1:36])
>>
>> plot(x, y, pch=18, type="p", ylab="yfoo", xlab="xfoo", yaxs="r")
>>
>> abline(h=100, v=0, col="gray60", lty=2)
>> text.xvalue<-151500
>> text.xvalue<-strptime(text.xvalue, format="%H%M%S")
>> text(text.xvalue, 80, "detection threshold", col="gray60", cex=0.8)
>>
>> event.1<-152833
>> event.1<-strptime(event.1, format="%H%M%S")
>> abline(v=event.1, col="red")
>>
>>
>
> The format for the xvalues works in the case of text positioning, but
> doesn't in the case of abline.
>
> JimHoltman replied this topic via email with a solution:
>
> <-as.POSIXct(strptime(y, format="%H%M%S"))
>
>
> I still don't know why this second function is necessary since everything
> works without it, except for the abline-thing...
>
> Nevertheless, thanks for all the suggestions!
>
> Fritz
> --
> View this message in context: http://www.nabble.com/abline%28v%3D-x%29-in-plot-with-time-formated-xaxis-not-working-tp24505884p24558044.html
> Sent from the R help mailing list archive at Nabble.com.
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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