R: Class "STTDF"

STTDF-class {spacetime} | R Documentation

## Class "STTDF"

### Description

A class for spatio-temporal trajectory data

### Usage

      ## S4 method for signature 'STTDF,ltraj'
    coerce(from, to, strict=TRUE)
      ## S4 method for signature 'ltraj,STTDF'
    coerce(from, to, strict=TRUE)

### Arguments

`from` | from object
`to` | target class
`strict` | ignored

### Objects from the Class

Objects of this class carry sparse (irregular) space/time data

### Slots

`sp`:

  Object of class `"Spatial"`, containing the bounding box of all trajectories

`time`:

  Object of class `"xts"`, containing the temporal bounding box of all trajectories

`traj`:

  Object of class `list`, each element holding an STI object reflecting a single trajectory;

`data`:

  Object of class `data.frame`, which holds the data values for each feature in each trajectory

### Methods

[

  `signature(x = "STTDF")`: select trajectories, based on index, or spatial and/or temporal predicates

### Note

The `data.frame` needs to have a column called `burst` which is a factor (or character) and contains the grouping of observations that come from a continuous sequence of observations. In addition, a column `id` is used to identify individual items.

### Author(s)

Edzer Pebesma, edzer.pebesma@uni-muenster.de

### References

http://www.jstatsoft.org/v51/i07/

### Examples

    library(sp)
    m = 3# nr of trajectories
    n = 100 # length of each
    l = vector("list", m)
    t0 = as.POSIXct("2013-05-05",tz="GMT")
    set.seed(1331) # fix randomness
    for (i in 1:m) {
        x = cumsum(rnorm(n))
        y = cumsum(rnorm(n))
        sp = SpatialPoints(cbind(x,y))
        #t = t0 + (0:(n-1) + (i-1)*n) * 60
        t = t0 + (0:(n-1) + (i-1)*n/2) * 60
        l[[i]] = STI(sp, t)
    }
    stt= STT(l)
    sttdf = STTDF(stt, data.frame(attr = rnorm(n*m), id = paste("ID", rep(1:m, each=n))))
    x = as(stt, "STI")
    stplot(sttdf, col=1:m, scales=list(draw=TRUE))
    stplot(sttdf, by = "id")
    stplot(sttdf[1])
    stplot(sttdf[1])

    # select a trajectory that intersect with a polygon
    p = Polygon(cbind(x=c(-20,-15,-15,-20,-20),y=c(10,10,15,15,10)))
    pol=SpatialPolygons(list(Polygons(list(p), "ID")))
    if (require(rgeos)) {
      stplot(sttdf[pol])
      names(sttdf[pol]@traj)
      stplot(sttdf[1:2],col=1:2)
      stplot(sttdf[,t0])
      stplot(sttdf[,"2013"])
      stplot(sttdf[pol,"2013"])
      is.null(sttdf[pol,t0])
    }

[Package spacetime version 1.2-2 Index]