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

[Petr PIKAL]

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 at 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
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> > > > > PLEASE do read the posting guide 
> > > > http://www.R-project.org/posting-guide.html
> > > > > and provide commented, minimal, self-contained, reproducible 
code.
> > > 
> > > 
> > > --
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> > > 
> > >
> 
> 
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