cut.trip: Split trip events into exact time-based boundaries.

Description

Split trip events within a single object into exact time boundaries, adding interpolated coordinates as required.

Usage

## S3 method for class 'trip':
cut(x, breaks, ...)

Arguments

A trip object.

breaks

A character string such as the breaks argument for cut.POSIXt, or alternatively a vector of date-time boundaries. (If the latter hese must encompass all the time range of the entire trip

...

Unused arguments.

Value

A list of trip objects, named by the time boundary in which they lie.

Details

Motion between boundaries is assumed linear and extra coordinates are added at the cut points. This function was completely rewritten in version 1.1-20.

Examples

Run this code

set.seed(66)
d <- data.frame(x=1:100, y=rnorm(100, 1, 10),
                tms= as.POSIXct(as.character(Sys.time()), tz = "GMT") + c(seq(10, 1000, length=50),
                seq(100, 1500, length=50)), id=gl(2, 50))
coordinates(d) <- ~x+y
tr <- trip(d, c("tms", "id"))

cut(tr, "200 sec")

bound.dates <- seq(min(tr$tms) - 1, max(tr$tms) + 1, length=5)
trip.list <- cut(tr, bound.dates)
bb <- bbox(tr)
cn <- c(20, 8)
g <- GridTopology(bb[, 1], apply(bb, 1, diff) / (cn - 1), cn)

tg <- tripGrid(tr, grid=g)
tg <- as.image.SpatialGridDataFrame(tg)
tg$x <- tg$x - diff(tg$x[1:2]) / 2
tg$y <- tg$y - diff(tg$y[1:2]) / 2

op <- par(mfcol=c(4, 1))
for (i in 1:length(trip.list)) {
  plot(coordinates(tr), pch=16, cex=0.7)
  title(names(trip.list)[i], cex.main=0.9)
  lines(trip.list[[i]])
  abline(h=tg$y, v=tg$x, col="grey")
  image(tripGrid(trip.list[[i]], grid=g), interpolate=FALSE,
  col=c("white", grey(seq(0.2, 0.7,  length=256))),add=TRUE)
  abline(h=tg$y, v=tg$x,  col="grey")
  lines(trip.list[[i]])
  points(trip.list[[i]], pch=16, cex=0.7)
}

par(op)
print("you may need to resize the window to see the grid data")

cn <- c(200, 80)
g <- GridTopology(bb[, 1], apply(bb, 1, diff) / (cn - 1), cn)

tg <- tripGrid(tr, grid=g)
tg <- as.image.SpatialGridDataFrame(tg)
tg$x <- tg$x - diff(tg$x[1:2]) / 2
tg$y <- tg$y - diff(tg$y[1:2]) / 2

op <- par(mfcol=c(4, 1))
for (i in 1:length(trip.list)) {
  plot(coordinates(tr), pch=16, cex=0.7)
  title(names(trip.list)[i], cex.main=0.9)
  image(tripGrid(trip.list[[i]], grid=g, method="density", sigma=1),
        interpolate=FALSE,
        col=c("white", grey(seq(0.2, 0.7, length=256))),
        add=TRUE)
  lines(trip.list[[i]])
  points(trip.list[[i]], pch=16, cex=0.7)
}

par(op)
print("you may need to resize the window to see the grid data")