STP_Track: STP_Track class

In markvregel/STPtrajectories: Space-time prism trajectories

Description

A class to represent Space-Time Prism(STP) trajecories. These are trajectories with a maximum speed for each segment. The maximum speed is added to the connections slot of class Track. The STP_Track can also combined in classes Tracks and TracksCollection of the trajecories package. The STP_Track method can be used to create a STP_Track from a Track of the trajectories package.

Usage

STP_Track(track, vmax, activity_time = 0, location_uncertainty = 0,
  time_uncertainty = 0)

Arguments

vmax	The maxium speed of the individual. Must be large enough to reach the next point. Either one vmax for entire track or a vector with the max speed for each segment.
activity_time	Time of an activity in minutes. During this the time the individual cannot move. Either one activity_time for entire track or a vector with the activity_time for each segment.
location_uncertainty	Uncertainty of the location of the space-time points in meters. Either one location_uncertainty for entire track or a vector with the location_uncertainty for each point.
time_uncertainty	Uncertainty of the time of the space-time points in minutes. Either one time_uncertainty for entire track or a vector with the time_uncertainty for each point.
Track	Object of class Track

Slots of class "Track"

sp:

spatial locations of the track points, with length n

time:

time stamps of the track points

endTime:

end time stamps of the track points

data:

data.frame with n rows, containing attributes of the track points

connections:

data.frame, with n-1 rows, containing attributes between the track points such as distance and speed

See Also

trajecotries package :https://cran.rstudio.com/web/packages/trajectories/index.html

Examples

library(spacetime)
library(sp)
#--------------------------create a STP_Track--------------------------
#------------------------------example 1------------------------------
## create trajectory data
t1 <- as.POSIXct(strptime("01/01/2017 12:00:00", "%m/%d/%Y %H:%M:%S"))
t2 <- as.POSIXct(strptime("01/7/2017 12:00:00", "%m/%d/%Y %H:%M:%S"))
time <- seq(t1,t2,2*60*60)
n <- length(time)
x = cumsum(runif(n) * 8000)
y = smooth(cumsum(runif(n,-0.7,1) * 16000))

crs_NL = CRS("+init=epsg:28992")

points <- SpatialPoints(cbind(x,y),crs_NL)

temp <-18 + cumsum(runif(n,-0.3,0.25))
altitude <- 200 + cumsum(runif(n,-0.75,1)*50)

data <- data.frame(temperature = temp, elevation = altitude)
## create a STP_track
# create class STIDF
stidf1 = STIDF(points, time, data)

# Track-class {trajectories}
my_track1<-Track(stidf1)

# set maximum speed
v1<-10/3.6# speed 10 km/h = 2.777778 m/s

# STP_track class
STP_track1<-STP_Track(my_track1,v1)
# plot
plot(STP_track1,type='p',pch=19,cex=0.8)
# calculate PPA and add to plot
PPA<-PPA(STP_track1)
plot(PPA,add=TRUE)

#------------------------------example 2------------------------------
## vmax depends on elevation
# assuming that max speed is lower as result of the thinner air
vmax<- getVmaxtrack(STP_track1) + (max(STP_track1@data$elevation[1:n-1])-STP_track1@data$elevation[1:n-1])*0.01
STP_track1@connections$vmax<-vmax
# calculate PPA
PPA<-PPA(STP_track1)
# create tracksCollection and plot
tracks = Tracks(list(tr1 = STP_track1))
tracksCollection = TracksCollection(list(tr = tracks))
stplot(tracksCollection, attr = "elevation", lwd = 3, scales = list(draw =TRUE),
      sp.layout=PPA,xlim = PPA@bbox[1,],ylim = PPA@bbox[2,],main= "Track with PPA\n vmax depends on altitude",
      sub='colour is altitude in meters',xlab='x',ylab='y')
#------------------------------example 3------------------------------
## vmax depends on the distance to get to next point.
# Thus on the distance that needs to be covered in the avialable time
# Assuming that if two points are closer together the max speed is lower
STP_track1@connections$vmax<-STP_track1@connections$speed*1.5
# calculate PPA
PPA<-PPA(STP_track1)
# create tracksCollection and plot
plot(PPA,add=TRUE)
tracks = Tracks(list(tr1 = STP_track1))
tracksCollection = TracksCollection(list(tr = tracks))
stplot(tracksCollection, attr = "vmax", lwd = 3, scales = list(draw = TRUE),
      sp.layout=PPA,xlim = PPA@bbox[1,],ylim = PPA@bbox[2,],
      main= "Track with PPA\n vmax depends on the distance and time budget between consecutive points",
      sub='colour is vmax in m/s',xlab='x',ylab='y',cex.main = 0.75)


#--------------------------subset a STP_Track--------------------------
# make sure vmax is high enough
STP_track1@connections$vmax<-getVmaxtrack(STP_track1)+1
#------------------------------example 1------------------------------
## subset based on space-time points
# get first 10 points
STP_track1_10<-STP_track1[1:10,'']
# only keep every second point
STP_track1_depleted<-STP_track1[seq(1,n,2),'']
plot(STP_track1,type='b')
plot(STP_track1_depleted,type='b')
#------------------------------example 2------------------------------
## subset based on time
STP_track1_a<-STP_track1[1:n,'2017-01-01 12:00:00 CET::2017-01-02 16:00:00 CET']
# only keep every second point within the time interval
STP_track1_b<-STP_track1[seq(1,n,2),'2017-01-01 12:00:00 CET::2017-01-02 16:00:00 CET']
# all points in the night(between 22:00 and 08:00)
STP_track1_c<-STP_track1[1:n,"T22:00/T08:00"] # see package xts for more handy subsetting tricks

markvregel/STPtrajectories documentation built on May 21, 2019, 12:25 p.m.