[R] time series with quality codes

[Achim Zeileis]

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 / °ÂʡΩ
> 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
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>
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