[R] ZOO: Learning to apply it to my data

Rich Shepard rshepard at appl-ecosys.com
Wed Sep 14 01:36:26 CEST 2011

On Tue, 13 Sep 2011, Gabor Grothendieck wrote:

> As in ?zoo a zoo object is a numeric matrix, numeric vector or factor
> together with an ordered time index which is unique. Its not clear that
> that is what you have; however, if we can assume that for each value of
> param we have a unique set of dates then quant could form a multivariate
> zoo series with Date index.


   Perhaps, then, zoo is not the appropriate library for my needs. Let me try
to clarify; being new to R and certainly new to zoo I may not express myself
clearly to those of you who are more experienced.

   On a given date (sampdate) and a given stream (aggregated from multiple
locations on that stream) a water sample was sent to the laboratory and
analyzed for a set of chemicals (param). Each param does not have a unique
set of dates. As my example showed, on 2010-06-30 SO4, Zn, and As
concentrations were measured on Winters Creek. On 2011-06-06, Cl, SO4, and
Zn concentrations were measured on the same stream.

> Read over ?zoo and ?read.zoo and also the 5 vignettes.  The zoo-read
> vignette is entirely about read.zoo. If you really do want to keep all
> that info you might want to use a data frame instead or possibly several
> zoo objects.

   The data are already in a data.frame and I need both factors and the date
to interpret the numeric values.

   I read ?zoo, but not ?read.zoo. I'll have to search for the vignettes.



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