Aggregate flows throughout a network based on an input matrix of flows
between all pairs of from
and to
points.
dodgr_flows_aggregate(graph, from, to, flows, contract = FALSE, heap = "BHeap", quiet = TRUE)
graph 


from  Vector or matrix of points from which aggregate flows are to be calculated (see Details) 
to  Vector or matrix of points to which aggregate flows are to be calculated (see Details) 
flows  Matrix of flows with 
contract  If 
heap  Type of heap to use in priority queue. Options include
Fibonacci Heap (default; 
quiet  If 
Modified version of graph with additonal flow
column added.
graph < weight_streetnet (hampi) from < sample (graph$from_id, size = 10) to < sample (graph$to_id, size = 5) to < to [!to %in% from] flows < matrix (10 * runif (length (from) * length (to)), nrow = length (from)) graph < dodgr_flows_aggregate (graph, from = from, to = to, flows = flows) # graph then has an additonal 'flows` column of aggregate flows along all # edges. These flows are directed, and can be aggregated to equivalent # undirected flows on an equivalent undirected graph with: graph_undir < merge_directed_flows (graph) # This graph will only include those edges having nonzero flows, and so: nrow (graph); nrow (graph_undir) # the latter is much smaller#> [1] 5973#> [1] 845# The following code can be used to convert the resultant graph to an `sf` # object suitable for plotting# NOT RUN { geoms < dodgr_to_sfc (graph_undir) gc < dodgr_contract_graph (graph_undir) gsf < sf::st_sf (geoms) gsf$flow < gc$flow # example of plotting with the 'mapview' package library (mapview) flow < gsf$flow / max (gsf$flow) ncols < 30 cols < colorRampPalette (c ("lawngreen", "red")) (ncols) [ceiling (ncols * flow)] mapview (gsf, color = cols, lwd = 10 * flow) # }# An example of flow aggregation across a generic (nonOSM) highway, # represented as the `routes_fast` object of the \pkg{stplanr} package, # which is a SpatialLinesDataFrame containing commuter densities along # components of a street network.# NOT RUN { library (stplanr) # merge all of the 'routes_fast' lines into a single network r < overline (routes_fast, attrib = "length", buff_dist = 1) r < sf::st_as_sf (r) # then extract the start and end points of each of the original 'routes_fast' # lines and use these for routing with `dodgr` l < lapply (routes_fast@lines, function (i) c (sp::coordinates (i) [[1]] [1, ], tail (sp::coordinates (i) [[1]], 1))) l < do.call (rbind, l) xy_start < l [, 1:2] xy_end < l [, 3:4] # Then just specify a generic OD matrix with uniform values of 1: flows < matrix (1, nrow = nrow (l), ncol = nrow (l)) # We need to specify both a `type` and `id` column for the # \link{weight_streetnet} function. r$type < 1 r$id < seq (nrow (r)) graph < weight_streetnet (r, type_col = "type", id_col = "id", wt_profile = 1) f < dodgr_flows_aggregate (graph, from = xy_start, to = xy_end, flows = flows) # Then merge directed flows and convert to \pkg{sf} for plotting as before: f < merge_directed_flows (f) geoms < dodgr_to_sfc (f) gc < dodgr_contract_graph (f) gsf < sf::st_sf (geoms) gsf$flow < gc$flow # sf plot: plot (gsf ["flow"]) # }