Nothing
Df2SpLines <-
function( df, crs=NA )
{
# This function converts an object of type data frame, calculated by the function
# ProcTraj, into an object of type Spatial Lines.
#
# Args:
# df: Data Frame Object created by the function ProcTraj.
# crs: String: Valid projection string. An example would be crs= "+proj=longlat +datum=NAD27"
#
# Results:
# Returns an object of class SpatialLines.
if( !is.na(crs) ){
crs <- CRS(crs)
}
max.traj.length <- max(abs(df$hour.inc)) + 1
if(nrow(df) %% max.traj.length != 0) {
stop("The number of rows in the 'df' argument is not a multiple of the length of an individual trajectory" )
}
# create a traj ID column to identify each trajctory uniquely
df['ID'] <- rep(1:(nrow(df) / max.traj.length), each=max.traj.length )
CreateLines <- function(df) {
# get the coordinates out of the data.frame
cc <- df[7:8]
# reverse the order of the columns from [Lat Long] to [Long Lat]
cc <- cc[, c(2, 1)]
# create a individual line
line <- Line(cc)
# transfor the line [line] into a Lines object and assign a unique ID
Lines(line, ID=as.character(df$ID[1]))
}
lines.list <- dlply( df, 'ID', CreateLines)
sp.lines <- SpatialLines(lines.list, proj4string = crs)
sp.lines
}
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