flows.R
In dodgr: Distances on Directed Graphs

## ----pkg-load, echo = FALSE, message = FALSE----------------------------------
library (dodgr)

## -----------------------------------------------------------------------------
graph <- weight_streetnet (hampi, wt_profile = "foot")
set.seed (1)
from <- sample (graph$from_id, size = 10)
to <- sample (graph$to_id, size = 10)
flows <- matrix (10 * runif (length (from) * length (to)),
    nrow = length (from)
)

## -----------------------------------------------------------------------------
graph_f <- dodgr_flows_aggregate (graph, from = from, to = to, flows = flows)
head (graph_f)

## -----------------------------------------------------------------------------
summary (graph_f$flow)

## -----------------------------------------------------------------------------
dens <- rep (1, length (from)) # uniform densities
graph_f <- dodgr_flows_disperse (graph, from = from, dens = dens)
summary (graph_f$flow)

## -----------------------------------------------------------------------------
graph_undir <- merge_directed_graph (graph_f)

## -----------------------------------------------------------------------------
nrow (graph_f)
nrow (graph_undir) # the latter is much smaller

## -----------------------------------------------------------------------------
graph <- graph [graph_undir$edge_id, ]
graph$flow <- graph_undir$flow

## ----flowmap, eval = FALSE----------------------------------------------------
#  graph_f <- graph_f [graph_f$flow > 0, ]
#  dodgr_flowmap (graph_f, linescale = 5)

## ----flows_si_map1-png, echo = FALSE, eval = FALSE----------------------------
#  graph_f <- dodgr_flows_si (graph, from = from, to = to)
#  graph_undir <- merge_directed_graph (graph_f)
#  graph <- graph [graph_undir$edge_id, ]
#  graph$flow <- graph_undir$flow
#  graph_f <- graph_f [graph_f$flow > 0, ]
#  png (file.path (here::here (), "vignettes", "hampi-flowmap2.png"),
#      width = 480, height = 480, units = "px"
#  )
#  dodgr_flowmap (graph_f, linescale = 5)
#  dev.off (which = dev.cur ())

## ----flows_si_map1, eval = FALSE----------------------------------------------
#  graph_f <- dodgr_flows_si (graph, from = from, to = to)
#  graph_undir <- merge_directed_graph (graph_f)
#  graph <- graph [graph_undir$edge_id, ]
#  graph$flow <- graph_undir$flow
#  graph_f <- graph_f [graph_f$flow > 0, ]
#  dodgr_flowmap (graph_f, linescale = 5)

## ----flows_si_map2-png, echo = FALSE, eval = FALSE----------------------------
#  graph <- weight_streetnet (hampi, wt_profile = "foot")
#  graph_f <- dodgr_flows_si (graph, from = from, to = to, k = 1e6)
#  graph_undir <- merge_directed_graph (graph_f)
#  graph <- graph [graph_undir$edge_id, ]
#  graph$flow <- graph_undir$flow
#  graph_f <- graph_f [graph_f$flow > 0, ]
#  png (file.path (here::here (), "vignettes", "hampi-flowmap3.png"),
#      width = 480, height = 480, units = "px"
#  )
#  dodgr_flowmap (graph_f, linescale = 5)
#  dev.off (which = dev.cur ())

## ----flows_si_map2, eval = FALSE----------------------------------------------
#  graph <- weight_streetnet (hampi, wt_profile = "foot")
#  graph_f <- dodgr_flows_si (graph, from = from, to = to, k = 1e6)
#  graph_undir <- merge_directed_graph (graph_f)
#  graph <- graph [graph_undir$edge_id, ]
#  graph$flow <- graph_undir$flow
#  graph_f <- graph_f [graph_f$flow > 0, ]
#  dodgr_flowmap (graph_f, linescale = 5)