[R] bug in axis.Date? was (Re: newbie needs help plotting time series)

From: Petr PIKAL <petr.pikal_at_precheza.cz>
Date: Wed, 02 Jul 2008 10:03:57 +0200

Hi

"Kathi" <kathi_at_dropnet.ch> napsal dne 01.07.2008 18:48:47:

> On Tue, 1 Jul 2008 14:33:12 +0200, Petr PIKAL wrote
> > "Kathi" <kathi@dropnet.ch> napsal dne 01.07.2008 13:39:18:
> >
> > > Thanks, Petr.
> > >
> > > After fiddling around some more with my code I found out that this
seems
> > to
> > > have something to do
> > > with the number of records the table I'm reading (here: column
B112).
> > Somehow,
> > > changing the
> > > number of records for B112 changes the numbers in the error message
-
> > though I
> > > don't quite
> > > understand how the number of records influences the axis intervals
or
> > their
> > > labels, since I define
> > > those explicitly...
> >
> > Neither I. So I sent it to r-help maybe somebody else will know. If
> > you debug code of axis.Date you find that after some computing there
> > is this comparison where range is based on your input data (in your
> > case x), and z is from defined at sequence of dates.
> >
> > z <- z[z >= range[1] & z <= range[2]]
> >
> > and this comparison results in character(0), when plotting with this
> > artificial example.
> >
> > plot(1:100, seq(405,410,length=100), axes=FALSE, ylim=c(405,410),
> > col="red", pch=15,
> > type="o", ylab="metres above sea level", main="Main Plot Title")
> > axis(2, at=405:410, tck=1, col="gray60")
> > axis.Date(1, at=seq(as.Date("2004-01-01"), as.Date("2008-06-01"),
> > by="month"), labels=seq(as.Date("2004-01-01"), as.Date("2008-06-01"),
> > by="month"), tck=1, col="gray60")
> >
> > I presume, that your x is from different interval of dates or it is
> > not a date.
>

> My data comes from a groundwater monitoring program. Once a month the
water surface is
> measured in some 170 stations, and I've been using R to visualize these
> measurements. In this
> particular case, the water table ranges between approximately 406 and
408
> metres above sea level,
> hence the y axis interval between 405 and 410.
> The values of my column x are dates of the format YYYY-MM-DD. If
something
> were wrong there,
> then I guess I would not be able to plot my data at all. But using the
limits
> of 2004-01-01 and
> 2008-06-01, I can plot all the timelines for my 170 measuring stations
without
> any problem. But
> since it's now July, I wanted to shift the view by half a year. So I
used
> "search and replace" in my code
> to change to 2004-07-01 and 2008-12-01 (plus six months in both cases).
That's
> when I got the
> error. I almost have a feeling that R doesn't like the "empty" part of
the
> graph for July-December... I
> don't understand why this happens, but maybe it has something to do with
the
> comparison of ranges
> you mentioned.

OK, It seems that you are right. Maybe you could add some expected x date/time values so that x axis will have no NA values.

x<-seq(as.Date("2004-01-01"), as.Date("2008-06-01"),by="month") y <- seq(405,410,length=54)
y[50:54] <-NA
plot(x, y, axes=FALSE, ylim=c(405,410),col="red", pch=15, type="o", ylab="metres above sea level", main="Main Plot Title") axis(2, at=405:410, tck=1, col="gray60")

axis.Date(1, at=seq(as.Date("2004-01-01"), as.Date("2008-06-01"),
by="month"), labels=seq(as.Date("2004-01-01"), as.Date("2008-06-01"),
by="month"), tck=1, col="gray60")

as you see, then everything works. However I think that it is pretty close to bug in axis.Date, maybe somebody can enlighten us both :-)

Regards
Petr

>
> Thanks for all your help!

>
> Kathi
>
> >
> > Regards
> > Petr
> >
> > >
> > > Kathi
> > >
> > >
> > > On Mon, 30 Jun 2008 11:48:43 +0200, Petr PIKAL wrote
> > > > Hi
> > > >
> > > > r-help-bounces_at_r-project.org napsal dne 30.06.2008 11:14:48:
> > > >
> > > > > Dear R help list
> > > > >
> > > > > I have recently started using R to visualize time series of
water
> > level
> > > > > measurements. The code I wrote
> > > > > does exactly what I want:
> > > > >
> > > > > plot(x, a$B112, axes=FALSE, ylim=c(405,410), col="red", pch=15,
> > > > > type="o", ylab="metres above sea level", main="Main Plot Title")
> > > > > axis(2, at=405:410, tck=1, col="gray60")
> > > > > axis.Date(1, at=seq(as.Date("2004-01-01"),
as.Date("2008-06-01"),
> > > > > by="month"), labels=seq(as.Date("2004-01-01"),
> > as.Date("2008-06-01"),
> > > > > by="month"), tck=1, col="gray60")
> > > > >
> > > > > Now I wanted to shift the data visualized by 6 months, so I
replaced
> >
> > > > > "2004-01-01" by "2004-07-01"
> > > > > and "2008-06-01" by "2008-12-01". Instead of the desired plot, I
get
> > an
> > > > error
> > > > > message stating
> > > > > (forgive the perhaps faulty translation into English, I'm
working on
> > a
> > > > German
> > > > > version of R):
> > > > >
> > > > > mistake in axis(side, at = z, labels = labels, ...) :
> > > > > length of 'at' and 'labels' different, 50 != 54
> > > >
> > > > Those two calls have different length
> > > >
> > > > at=seq(as.Date("2004-01-01"), as.Date("2008-06-01"), by="month")
> > > > labels=seq(as.Date("2004-01-01"), as.Date("2008-06-01"),
by="month")
> > > >
> > > > you can try it by
> > > >
> > > > length(seq(...))
> > > >
> > > > could not there be some typo in your call?
> > > >
> > > > Regards
> > > >
> > > > Petr
> > > >
> > > > >
> > > > > What have I done wrong? Thank you very much for your help!
> > > > >
> > > > > Katharina Dubach
> > > > >
> > > > > ______________________________________________
> > > > > 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.
> > >
> > >
> > > --
> > > DropNet AG - Das Unternehmen fuer Ihren Internet-Auftritt!
> > >
> > >
>
>
> --
> DropNet AG - Das Unternehmen fuer Ihren Internet-Auftritt!
>
>



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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. Received on Wed 02 Jul 2008 - 08:13:24 GMT

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