[R-sig-Geo] Extend spacetime ST

[Edzer Pebesma]

Chris, I'd use the following for a class "watch_circ" that extends ST
and adds a character ID slot:

> setClass("watch_circ", contains = "ST", slots = c(ID = "character"))
> showClass("watch_circ")
Class "watch_circ" [in ".GlobalEnv"]

Slots:

Name:         ID        sp      time   endTime
Class: character   Spatial       xts   POSIXct

Extends: "ST"
>

On 06/06/2015 07:58 AM, chris english wrote:
> Hi,
> 
> I am attempting to extent spacetime ST to include an ID class for a
> spacetime watch circle object.  I am doing this in order to be able to
> relatively easily test that I have unique ID(s) across several similar
> objects for plotting purposes.
> 
> I can build my watch circle:
> 
>> setClass("watch_circ",
> + slots = c(sp = "Spatial", time = "xts", ID = "character",
> + endTime = "POSIXct"),
> + validity = function(object) {
> + stopifnot(length(object at sp) >= 1)
> + stopifnot(nrow(object at time) >= 1)
> + stopifnot(is.char(object at ID))
> + stopifnot(nrow(object at time) == length(object at endTime))
> + # do the tzones if not set, if set
> + tz1 = attr(object at time, "tzone")
> + tz2 = attr(object at emdTime, "tzone")
> + tz1.set = (!is.null(tz1) && !nchar(tz1)==0)
> + tz2.set = (!is.null(tz2) && !nchar(tz2)==0)
> + stopifnot(tz1 == tz2)
> + if (tz1.set)
> + stopifnot(tz1 == tz2)
> + if (any(names(object at time) %in% names(object at sp)))
> + stop("name conflict: attribute names in sp and time slot must differ")
> + return(TRUE)
> + }
> + )
>> getClassDef('watch_circ')
> Class "watch_circ" [in ".GlobalEnv"]
> 
> Slots:
> 
> Name:         sp      time        ID   endTime
> Class:   Spatial       xts character   POSIXct
> 
> But not extend ST.
> 
>> setClass("watch_circ_1", representation = "ST")
>> getClassDef('watch_circ_1')
> Class "watch_circ_1" [in ".GlobalEnv"]
> 
> Slots:
> 
> Name:       sp    time endTime
> Class: Spatial     xts POSIXct
> 
> Extends: "ST"
>> ?what am I doing wrong here?
> 
> This is probably due to my shallow understanding of the difference between
> slots and representation, and possibly this whole operation is unnecessary
> if plot checks sp for unique ID(s) among objects.
> 
> Thanks in advance,
> 
> Cheers,
> Chris
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi),  University of Münster,
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/
Spatial Statistics Society http://www.spatialstatistics.info

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