R/osm_highwaynodes_extract.R

In paleolimbot/rfuncs: Useful R Functions Accordin to paleolimbot

#' Extract highways from Open Street Map data
#' 
#' Uses the \code{osmar} package to fetch OSM data and extract only highway
#' nodes and ways.
#'
#' @param box A bounding box as generated by \code{prettymapr::searchbbox} or
#'   \code{osmar::center_bbox}
#' @param apisource An OSM api source as generated by the \code{osmar::osmsource_*}
#'   functions.
#'
#' @return An \code{osmar} object containing nodes and ways of highways.
#' @export
#'
#' @examples
#' wv <- prettymapr::searchbbox("wolfville, ns", source="google")
#' d2 <- osmdata_highways(wv)
#' 
osmdata_highways <- function(box, apisource=osmar::osmsource_api()) {
  if(class(box) == "matrix") {
    box <- c(box[1], box[2], box[3], box[4])
    names(box) <- c("left", "bottom", "right", "top")
    class(box) <- "bbox"
  }
  osmdata <- osmar::get_osm(box, source=apisource)
  hways_muc <- subset(osmdata, way_ids = osmar::find(osmdata, osmar::way(osmar::tags(k == "highway"))))
  hways <- osmar::find(hways_muc, osmar::way(osmar::tags(k == "name")))
  hways <- osmar::find_down(osmdata, osmar::way(hways))
  hways_muc <- subset(osmdata, ids = hways)
  #data.frame(hways_muc$nodes$attrs) to get lat/lons as data frame
  return(hways_muc)
}

#' Get the nearest OSM nodes to a point
#' 
#' Finds the nearest OSM node(s) to a lat/lon coordinate.
#'
#' @param osmarobj an \code{osmar} object
#' @param lon The longitude
#' @param lat The latitude
#' @param num The number of points to return
#'
#' @return a \code{list} containing the OSM data pertaining to the points as well
#'   as the computed distances
#' @export
#'
#' @examples
#' #use extract_highways to get highway data
#' wv <- prettymapr::searchbbox("wolfville, ns", source="google")
#' d2 <- osmdata_highways(wv)
#' 
#' #use nearest_nodes to get nearest road names to a location
#' nearesthwys <- osmdata_nearest_nodes(d2, -64.3557, 45.0857, num=10)
#' waysdata <- subset(d2, way_ids = nearesthwys$info$way_ids)
#' waynames <- unique(as.character(waysdata$ways$tags$v[waysdata$ways$tags$k=="name"]))
#' 
osmdata_nearest_nodes <- function(osmarobj, lon, lat, num=1) {
  ats <- osmarobj$nodes$attrs
  ats$dists <- geodist(ats$lon, ats$lat, lon, lat)
  ats <- ats[order(ats$dists,decreasing = FALSE),]
  node_id <- ats$id[1:num]
  dist <- ats$dists[1:num]
  return(list(info=osmar::find_up(osmarobj, osmar::node(node_id)), dist=dist))
}