make_lines.R

# fun with sp objects

library(sp)

set.seed(100)

n <- 8 
m <- rpois(lambda=2,n)+1 

x_range <- c(0,100)
y_range <- c(30,90)

x <- runif(n, min=x_range[1], max=x_range[2] )
y <- runif(n, min=y_range[1], max=x_range[2] )

core_points <- cbind(x,y,1:n)
colnames(core_points) <- c('x','y','label')

core_points_new <- c()
for( i in 1:n) {
  core_point <- matrix(rep(core_points[i,,drop=FALSE],each=m[i]),nrow=m[i])
  core_point <- cbind( core_point, 
    core_point[,1] + runif(m[i]), 
    core_point[,2] + runif(m[i])
   ) 

  core_points_new <- rbind(core_points_new, core_point)
}
colnames(core_points_new) <- c('x','y','label','x_local','y_local')


# create spatial lines
matrix_to_spatial_lines <- function( x, from, to, label ) {
  
  a <- list()

  if( missing(label) ) {
    for( i in 1:NROW(x) ) {
    a[[i]] <- Lines( list(Line( rbind( x[i,from], x[i,to] ) )), 
           ID=as.character(i) )
    }
  } else {

    for( i in 1:NROW(x) ) {
    a[[i]] <- Lines( list(Line( cbind( x[i,from], x[i,to] ) )), 
           ID=as.character(x[i,label]) )
    }
  }
  return( SpatialLines( a ) )
}

b <- matrix_to_spatial_lines(core_points_new, c('x_local','y_local'), c('x','y'))