[R] Calculation of daily max

[Gabor Grothendieck]

Assuming VDATE is a character vector this produces
a zoo time series object.

	library(zoo)
	z <- aggregate(zoo(WS), as.Date(VDATE), max)

coredata(z) and time(z) are the data vector of maximums and
corresponding times, respectively.

The R command:

               vignette("zoo")

gives an introduction to zoo.

Aside from zoo you could check out ?tapply, ?by and ?aggregate .



On 1/16/06, Augusto.Sanabria at ga.gov.au <Augusto.Sanabria at ga.gov.au> wrote:
>
> Good day everyone.
>
> I have a large dataset of 1 min wind speeds
> covering 5 years.
>
> How can I make an array of maximum daily values?
>
> The vectors I have are: 'VDATE' with dates in format
> '%Y-%m-%d' (like '1992-10-28') and 'WS' with wind speed data
> (same number of elements as VDATE).
>
> I want an array with 2 columns: Max daily wind speed and
> corresponding day.
>
> Has anyone got an elegant way of doing that?
> (My background is in C++ I would tend to use loops
> but that is not very elegant in R, isn't it?)
>
> Augusto
>
>
>
> --------------------------------------------
> Augusto Sanabria. MSc, PhD.
> Mathematical Modeller
> Risk Research Group
> Geospatial & Earth Monitoring Division
> Geoscience Australia (www.ga.gov.au)
> Cnr. Jerrabomberra Av. & Hindmarsh Dr.
> Symonston ACT 2609
> Ph. (02) 6249-9155
>
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