R/func_points_to_line.R

In willdrysdale/wsdmiscr: wsdmiscr

#' Points to Line
#' 
#' Converts XY points to a spatial lines object. Copied from https://rpubs.com/walkerke/points_to_line
#' 
#' @param data dataframe containing XY data
#' @param long name of longditude column
#' @param lat name of latitude column
#' 
#' @export

points_to_line <- function(data, long, lat, id_field = NULL, sort_field = NULL) {
  
  # Convert to SpatialPointsDataFrame
  coordinates(data) <- c(long, lat)
  
  # If there is a sort field...
  if (!is.null(sort_field)) {
    if (!is.null(id_field)) {
      data <- data[order(data[[id_field]], data[[sort_field]]), ]
    } else {
      data <- data[order(data[[sort_field]]), ]
    }
  }
  
  # If there is only one path...
  if (is.null(id_field)) {
    
    lines <- SpatialLines(list(Lines(list(Line(data)), "id")))
    
    return(lines)
    
    # Now, if we have multiple lines...
  } else if (!is.null(id_field)) {  
    
    # Split into a list by ID field
    paths <- sp::split(data, data[[id_field]])
    
    sp_lines <- SpatialLines(list(Lines(list(Line(paths[[1]])), "line1")))
    
    for (p in 2:length(paths)) {
      id <- paste0("line", as.character(p))
      l <- SpatialLines(list(Lines(list(Line(paths[[p]])), id)))
      sp_lines <- spRbind(sp_lines, l)
    }
    
    return(sp_lines)
  }
}