kmlShape (version 0.9.5)

reduceNbTimes: ~ Function: reduceNbTimes ~

Description

reduceNbTimes simplify some trajectories (in long format) by reducing their number of points.

Usage

reduceNbTimes(trajLong, nbPoints, spar=NA)

Arguments

trajLong

[data.frame]: data.frame that hold the trajectories in long format. The data.frame has to be (no choice!) in the following format: the first column should be the individual indentifiant. The second should be the times at which the measurement are made. The third one should be the measurement.

nbPoints

[numeric]: fixe the number of that the simplified trajectories should have.

spar

[numeric]: smoothing parameter that is used if the trajectories shall be smoothed before being simplified.

Value

A data.frame holding the simplified trajectories, in long format.

Details

reduceNbTimes simplify some trajectories by reducing their number of points. The trajectories should be in long format. If a value is given to spar (different from NA), trajectories are smoothed using smooth.spline.

The reduction of the number of point is done using a variation of Douglas-Peucker algorithme based on the number of points instead of an epsilon.

See Also

reduceNbTimes, DouglasPeuckerEpsilon, DouglasPeuckerNbPoints

Examples

  require(lattice)

  ### Some artificial data
  g <- function(x)dnorm(x,3)+dnorm(x,7)+x/10
  dn <- data.frame(id=rep(1:20,each=101),
    times=rep((0:100)/10,times=20),
    traj=rep(g((0:100)/10),20)+rep(runif(20),each=101)+rnorm(20*101,,0.1))

  xyplot(traj ~ times, data=dn, groups=id,type="l")

  ### Reduction to 50 points
  dn2 <- reduceNbTimes(trajLong=dn,nbPoints=50)
  xyplot(traj ~ times, data=dn2, groups=id,type="l")

  ### Reduction to 20 points
  dn3 <- reduceNbTimes(trajLong=dn,nbPoints=20)
  xyplot(traj ~ times, data=dn3, groups=id,type="l")

  ### Smoothing then reduction to 20 points
  dn4 <- reduceNbTimes(trajLong=dn,nbPoints=20,spar=0.5)
  xyplot(traj ~ times, data=dn4, groups=id,type="l")