Message-ID: <512B77F4.4000805@uni-muenster.de>
Date: 2013-02-25T14:40:52Z
From: Edzer Pebesma
Subject: Spatiotemporal inquiry
In-Reply-To: <CAK8gSG_X7qF+kSnzvHjzJCqf5fLkO2ODU5SJ=f=DrsevAodq8w@mail.gmail.com>
On 02/25/2013 02:24 PM, ping yang wrote:
> Dear R,
>
> I have a question for conducting a spatio-temporal inquiry, suppose I have
> a time series of air temperature data for 100 years for my domain, can I
> perform a inquiry like this " *How many days are there temperature above 40
> degree *(CC) and get all these days", I noticed there are evolving
> discussion on the space-time library, Have anyone already done this? or Any
> suggestions will be appreciated.
assuming you have regular time series for a limited number of weather
stations, then your question is similar to asking for the wind data set
how many days the wind speed exceeded e.g. the value of 19:
library(spacetime)
example(stConstruct)
sel = which(apply(as(wind.st, "xts"), 1, function(x) any(x > 19)))
length(sel)
# how many: 2416
unique(index(wind.st[,sel]))
# which dates: "1961-01-10 GMT" "1961-01-11 GMT" "1961-01-12 GMT" etc.
note that we're essentially counting rows in a matrix with some value(s)
larger than 19 here -- seeing the thing as a multivariate time series,
meaning you could do all this with xts or zoo alone.
>
> Thanks,
>
> Ping
>
> [[alternative HTML version deleted]]
>
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--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of M?nster
Weseler Stra?e 253, 48151 M?nster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics e.pebesma at wwu.de