mergeTrackObs: Merge two SpatialPoints or SpatialPointsDataFrame objects, one modelling a track, the other observations

Description

Merge two SpatialPoints or SpatialPointsDataFrame objects, one modelling a track, the other observations.

Usage

mergeTrackObs(sppdfInt,sppdfObs,obscol=NULL)

Arguments

sppdfInt

A SpatialPoints object (the track)

sppdfObs

A SpatialPoints or SpatialPointsDataFrame object (the observations)

obscol

The column number in which the number of observations at this point can be found in sppdfObs

Value

A SpatialPointsDataframe, with the following attributes:

ID ID number
nObs The number of observations in the interval

Details

Road site counts or faeces collections are often carried out along tracks (paths, roads, transects, etc.). Tracks can be discretized in regular intervals e.g. with transLines2pix or thintrack, each point being an interval centre. mergeTrackObs uses such a discretized track and sums observations to their nearest track interval. The output is a SpatialPointsDataFrame where each point corresponds to the centre of one track interval. The number of observations in each interval is given in the attribute file. If the number of observations at an observation point can be 0 or any positive number, use obscol to identify the column of sppdfObs where this number is stored.

Examples

Run this code

# NOT RUN {
    # track
    library(sp)
     l2 = cbind(c(1,2,3),c(1,1.5,1))
     Sl2 = Line(l2)
     S2 = Lines(list(Sl2), ID="b")
     Sl = SpatialLines(list(S2))
     plot(Sl, col = "blue")
    #observations
     obs <- structure(list(ID = 1:15, long = c(1.04609377280342, 1.0890625305741, 
1.08125002916125, 1.24921880953755, 1.34687507719818, 1.50312510545521, 
1.88984392539134, 2.37812526369453, 2.39375026652023, 2.36640651157525, 
2.38593776510738, 2.62031280749291, 2.69843782162142, 2.85078159917202, 
2.90546910906198), lat = c(1.04062476682306, 1.05624976964876, 
1.03671851611663, 1.13828103448369, 1.16562478942867, 1.26718730779574, 
1.43124983746561, 1.32968731909855, 1.32187481768569, 1.30624981485999, 
1.28281231062144, 1.20468729649293, 1.13828103448369, 1.08749977530016, 
1.03671851611663)), .Names = c("ID", "long", "lat"), row.names = c(NA, 
-15L), class = "data.frame")
    points(obs[,2:3],col="red")
    coordinates(obs)<-~long+lat
obs@data$n<-c(3,4,0,1,1,5,6,4,3,4,4,7,2,2,1) # possibly a count on each location


# examples

# one observation on each location
track<-transLines2pix(Sl,0.1)
trackObs<-mergeTrackObs(track,obs)

par(mfrow=c(1,2))
plot(Sl)
plot(track,add=TRUE,col="blue")
plot(obs,add=TRUE,col="red",pch=1)

plot(Sl)
plot(track,add=TRUE,col="blue")
plot(trackObs,cex=trackObs@data$nObs,pch=19, col="red",add=TRUE)


# 0 or more observations on each location
obs@data$n<-c(3,4,0,1,1,5,6,4,3,4,4,7,2,2,1) # possibly a count on each location
obs@data
trackObs<-mergeTrackObs(track,obs,obscol=2)

par(mfrow=c(1,2))
plot(Sl)
plot(track,add=TRUE,col="blue")
plot(obs,add=TRUE,col="red",pch=1)

plot(Sl)
plot(track,add=TRUE,col="blue")
plot(trackObs,cex=trackObs@data$nObs/3,pch=19, col="red",add=TRUE)

     
# }