[R] time series with quality codes

[Gabor Grothendieck]

In addition, we could create a function to.df which converts a zoo
object to a data frame assuming that any column that only contains
1:nlevels is a factor with the indicated level names.  Use to.df just
before plotting:

library(zoo)
set.seed(1)
f <- zoo(factor(sample(3, 10, replace = TRUE)))
x <- zoo(rnorm(10))
y <- zoo(rnorm(10))
z <- merge(x, y, f)

to.df <- function(z, levels = letters[1:3], time = FALSE) {
	zz <- as.data.frame(z)
	for(i in ncol(zz))
		if (all(zz[,i] %in% seq_along(levels)))
			z[,i] <- factor(levels[z[,i]])
	if (time) cbind(index = index(z), zz) else zz
}

library(lattice)
xyplot(y ~ x | f, data = to.df(z))




On 8/16/07, Achim Zeileis <Achim.Zeileis at wu-wien.ac.at> wrote:
> On Thu, 16 Aug 2007, Felix Andrews wrote:
>
> > list(...),
> >
> > I am working with environmental time series (eg rainfall, stream flow)
> > that have attached quality codes for each data point. The quality
> > codes have just a few factor levels, like "good", "suspect", "poor",
> > "imputed". I use the quality codes in plots and summaries. They are
> > carried through when a time series is aggregated to a longer
> > time-step, according to rules like "worst", "median" or "mode".
> >
> > I need to support time steps of anything from hours to years. I can
> > assume the data are regular time series -- they might be irregular
> > initially but could be 'regularized'. But I would want to plot
> > irregular time series along with regular ones.
> >
> > So far I have been using a data frame with a POSIXct column, a numeric
> > column and a factor column. However I would like to use zoo instead,
> > because of its many utility functions and easy conversion to ts. Is
> > there any prospect of zoo handling such numeric + factor data? Other
> > suggestions on elegant ways to do it are also welcome.
>
> There is some limited support for this in zoo. You can do
>   z <- zoo(myfactor, myindex)
> and work with it like a zoo series and then
>   coredata(z)
> will recover a factor. However, you cannot bind this to other series
> without losing the factor structure. At least not in a plain zoo series.
> But you can do
>   df <- merge(z, Z, retclass = "data.frame")
> where every column of the resulting data.frame is a univariate zoo series.
>
> The final option would be to just have a data.frame as usual and put your
> data/index into one column. But then it's more difficult to leverage zoo's
> functionality.
>
> I would like to have more support for things like this, but currently this
> is what we have.
>
> Best,
> Z
>
> > Felix
> >
> > --
> > Felix Andrews / ������
> > PhD candidate
> > Integrated Catchment Assessment and Management Centre
> > The Fenner School of Environment and Society
> > The Australian National University (Building 48A), ACT 0200
> > Beijing Bag, Locked Bag 40, Kingston ACT 2604
> > http://www.neurofractal.org/felix/
> > xmpp:foolish.android at gmail.com
> > 3358 543D AAC6 22C2 D336  80D9 360B 72DD 3E4C F5D8
> >
> > ______________________________________________
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> >
> >
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
>
>