Function is fully vectorized to calculate accept vectors of central points and vectors defining multiple isochrone thresholds.
Usage
dodgr_isochrones(
graph,
from = NULL,
tlim = NULL,
concavity = 0,
length_threshold = 0,
heap = "BHeap"
)
Arguments
- graph
data.frame
or equivalent object representing the network graph. Fordodgr
street networks, this must be a network derived from silicate ("sc") data, generated with weight_streetnet. This function does not work with networks derived from sf data.- from
Vector or matrix of points from which isochrones are to be calculated.
- tlim
Vector of desired limits of isochrones in seconds
- concavity
A value between 0 and 1, with 0 giving (generally smoother but less detailed) convex iso-contours and 1 giving highly concave (and generally more detailed) contours.
- length_threshold
The minimal length of a segment of the iso-contour to be made more convex according to the 'concavity` parameter.. Low values will produce highly detailed hulls which may cause problems; if in doubt, or if odd results appear, increase this value.
- 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
).
Value
A single data.frame
of isochrones as points sorted anticlockwise
around each origin (from
) point, with columns denoting the from
points
and tlim
value(s). The isochrones are given as id
values and associated
coordinates of the series of points from each from
point at the specified
isochrone times.
Isochrones are calculated by default using parallel computation with the
maximal number of available cores or threads. This number can be reduced by
specifying a value via RcppParallel::setThreadOptions (numThreads = <desired_number>)
.
Note
Isodists are calculated by default using parallel computation with the
maximal number of available cores or threads. This number can be reduced by
specifying a value via
RcppParallel::setThreadOptions (numThreads = <desired_number>)
.
See also
Other distances:
dodgr_distances()
,
dodgr_dists()
,
dodgr_dists_categorical()
,
dodgr_dists_nearest()
,
dodgr_flows_aggregate()
,
dodgr_flows_disperse()
,
dodgr_flows_si()
,
dodgr_isodists()
,
dodgr_isoverts()
,
dodgr_paths()
,
dodgr_times()
Examples
if (FALSE) { # \dontrun{
# Use osmdata package to extract 'SC'-format data:
library (osmdata)
dat <- opq ("hampi india") %>%
add_osm_feature (key = "highway") %>%
osmdata_sc ()
graph <- weight_streetnet (dat)
from <- sample (graph$.vx0, size = 100)
tlim <- c (5, 10, 20, 30, 60) * 60 # times in seconds
x <- dodgr_isochrones (graph, from = from, tlim)
} # }