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| Original file line number | Diff line number | Diff line change |
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| #' Calculate vector of shortest distances from a series of 'from' points to | ||
| #' nearest one of series of 'to' points. | ||
| #' | ||
| #' @param graph `data.frame` or equivalent object representing the network | ||
| #' graph (see Notes) | ||
| #' @param from Vector or matrix of points **from** which route distances are to | ||
| #' be calculated (see Notes) | ||
| #' @param to Vector or matrix of points **to** which shortest route distances | ||
| #' are to be calculated to nearest 'to' point only. | ||
| #' @param shortest If `FALSE`, calculate distances along the \emph{fastest} | ||
| #' rather than shortest routes (see Notes). | ||
| #' @param heap Type of heap to use in priority queue. Options include | ||
| #' Fibonacci Heap (default; `FHeap`), Binary Heap (`BHeap`), | ||
| #' `Trinomial Heap (`TriHeap`), Extended Trinomial Heap | ||
| #' (`TriHeapExt`, and 2-3 Heap (`Heap23`). | ||
| #' @param parallel If `TRUE`, perform routing calculation in parallel (see | ||
| #' details) | ||
| #' @param quiet If `FALSE`, display progress messages on screen. | ||
| #' @return Vector of distances, one element for each 'from' point giving the | ||
| #' distance to the nearest 'to' point. | ||
| #' | ||
| #' @note `graph` must minimally contain three columns of `from`, | ||
| #' `to`, `dist`. If an additional column named `weight` or | ||
| #' `wt` is present, shortest paths are calculated according to values | ||
| #' specified in that column; otherwise according to `dist` values. Either | ||
| #' way, final distances between `from` and `to` points are calculated | ||
| #' by default according to values of `dist`. That is, paths between any pair of | ||
| #' points will be calculated according to the minimal total sum of `weight` | ||
| #' values (if present), while reported distances will be total sums of `dist` | ||
| #' values. | ||
| #' | ||
| #' For street networks produced with \link{weight_streetnet}, distances may also | ||
| #' be calculated along the \emph{fastest} routes with the `shortest = FALSE` | ||
| #' option. Graphs must in this case have columns of `time` and `time_weighted`. | ||
| #' Note that the fastest routes will only be approximate when derived from | ||
| #' \pkg{sf}-format data generated with the \pkg{osmdata} function | ||
| #' `osmdata_sf()`, and will be much more accurate when derived from `sc`-format | ||
| #' data generated with `osmdata_sc()`. See \link{weight_streetnet} for details. | ||
| #' | ||
| #' The `from` and `to` columns of `graph` may be either single | ||
| #' columns of numeric or character values specifying the numbers or names of | ||
| #' graph vertices, or combinations to two columns specifying geographical | ||
| #' (longitude and latitude) coordinates. In the latter case, almost any sensible | ||
| #' combination of names will be accepted (for example, `fromx, fromy`, | ||
| #' `from_x, from_y`, or `fr_lat, fr_lon`.) | ||
| #' | ||
| #' `from` and `to` values can be either two-column matrices or | ||
| #' equivalent of longitude and latitude coordinates, or else single columns | ||
| #' precisely matching node numbers or names given in `graph$from` or | ||
| #' `graph$to`. If `to` is `NULL`, pairwise distances are calculated from all | ||
| #' `from` points to all other nodes in `graph`. If both `from` and `to` are | ||
| #' `NULL`, pairwise distances are calculated between all nodes in `graph`. | ||
| #' | ||
| #' Calculations in parallel (`parallel = TRUE`) ought very generally be | ||
| #' advantageous. For small graphs, calculating distances in parallel is likely | ||
| #' to offer relatively little gain in speed, but increases from parallel | ||
| #' computation will generally markedly increase with increasing graph sizes. | ||
| #' By default, parallel computation uses the maximal number of available cores | ||
| #' or threads. This number can be reduced by specifying a value via | ||
| #' `RcppParallel::setThreadOptions (numThreads = <desired_number>)`. Parallel | ||
| #' calculations are, however, not able to be interrupted (for example, by | ||
| #' `Ctrl-C`), and can only be stopped by killing the R process. | ||
| #' | ||
| #' @family distances | ||
| #' @export | ||
| #' @examples | ||
| #' # A simple graph | ||
| #' graph <- data.frame ( | ||
| #' from = c ("A", "B", "B", "B", "C", "C", "D", "D"), | ||
| #' to = c ("B", "A", "C", "D", "B", "D", "C", "A"), | ||
| #' d = c (1, 2, 1, 3, 2, 1, 2, 1) | ||
| #' ) | ||
| #' dodgr_dists (graph) | ||
| #' | ||
| #' # A larger example from the included [hampi()] data. | ||
| #' graph <- weight_streetnet (hampi) | ||
| #' from <- sample (graph$from_id, size = 100) | ||
| #' to <- sample (graph$to_id, size = 50) | ||
| #' d <- dodgr_dists (graph, from = from, to = to) | ||
| #' # d is a 100-by-50 matrix of distances between `from` and `to` | ||
| #' | ||
| #' \dontrun{ | ||
| #' # a more complex street network example, thanks to @chrijo; see | ||
| #' # https://github.com/ATFutures/dodgr/issues/47 | ||
| #' | ||
| #' xy <- rbind ( | ||
| #' c (7.005994, 51.45774), # limbeckerplatz 1 essen germany | ||
| #' c (7.012874, 51.45041) | ||
| #' ) # hauptbahnhof essen germany | ||
| #' xy <- data.frame (lon = xy [, 1], lat = xy [, 2]) | ||
| #' essen <- dodgr_streetnet (pts = xy, expand = 0.2, quiet = FALSE) | ||
| #' graph <- weight_streetnet (essen, wt_profile = "foot") | ||
| #' d <- dodgr_dists (graph, from = xy, to = xy) | ||
| #' # First reason why this does not work is because the graph has multiple, | ||
| #' # disconnected components. | ||
| #' table (graph$component) | ||
| #' # reduce to largest connected component, which is always number 1 | ||
| #' graph <- graph [which (graph$component == 1), ] | ||
| #' d <- dodgr_dists (graph, from = xy, to = xy) | ||
| #' # should work, but even then note that | ||
| #' table (essen$level) | ||
| #' # There are parts of the network on different building levels (because of | ||
| #' # shopping malls and the like). These may or may not be connected, so it may | ||
| #' # be necessary to filter out particular levels | ||
| #' index <- which (!(essen$level == "-1" | essen$level == "1")) # for example | ||
| #' library (sf) # needed for following sub-select operation | ||
| #' essen <- essen [index, ] | ||
| #' graph <- weight_streetnet (essen, wt_profile = "foot") | ||
| #' graph <- graph [which (graph$component == 1), ] | ||
| #' d <- dodgr_dists (graph, from = xy, to = xy) | ||
| #' } | ||
| dodgr_dists_nearest <- function (graph, | ||
| from = NULL, | ||
| to = NULL, | ||
| shortest = TRUE, | ||
| heap = "BHeap", | ||
| parallel = TRUE, | ||
| quiet = TRUE) { | ||
|
|
||
| graph <- tbl_to_df (graph) | ||
|
|
||
| hps <- get_heap (heap, graph) | ||
| heap <- hps$heap | ||
| graph <- hps$graph | ||
|
|
||
| graph <- preprocess_spatial_cols (graph) | ||
| gr_cols <- dodgr_graph_cols (graph) | ||
| is_spatial <- is_graph_spatial (graph) | ||
| to_from_indices <- to_from_index_with_tp (graph, from, to) | ||
| if (to_from_indices$compound) { | ||
| graph <- to_from_indices$graph_compound | ||
| } | ||
|
|
||
| if (!shortest) { | ||
| if (is.na (gr_cols$time_weighted)) { | ||
| stop ( | ||
| "Graph does not contain a weighted time column from ", | ||
| "which to calculate fastest paths." | ||
| ) | ||
| } | ||
| graph [[gr_cols$d_weighted]] <- graph [[gr_cols$time_weighted]] | ||
| } | ||
|
|
||
| graph <- convert_graph (graph, gr_cols) | ||
|
|
||
| if (!quiet) { | ||
| message ("Calculating shortest paths ... ", appendLF = FALSE) | ||
| } | ||
|
|
||
| if (parallel && heap == "TriHeapExt") { | ||
| if (!quiet) { | ||
| message ( | ||
| "Extended TriHeaps can not be calculated in parallel; ", | ||
| "reverting to serial calculation" | ||
| ) | ||
| } | ||
| parallel <- FALSE | ||
| } | ||
|
|
||
| d <- rcpp_get_sp_dists_nearest ( | ||
| graph, | ||
| to_from_indices$vert_map, | ||
| to_from_indices$from$index, | ||
| to_from_indices$to$index, | ||
| heap | ||
| ) | ||
| index <- seq_along (to_from_indices$from$index) | ||
| nearest_index <- as.integer (d [index + length (index)]) | ||
| d <- d [index] | ||
| nearest_index <- match (nearest_index, to_from_indices$to$index) | ||
| nearest_ids <- to_from_indices$to$id [nearest_index] | ||
| nearest_ids <- gsub ("\\_(start|end)$", "", nearest_ids) | ||
|
|
||
| return (data.frame ( | ||
| from = to_from_indices$from$id, | ||
| to = nearest_ids, | ||
| d = d, | ||
| stringsAsFactors = FALSE | ||
| )) | ||
| } |
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