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
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Edzer Pebesma
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