valhallr (version 0.1.0)

od_table: Generate Tidy Origin-Destination Data using Valhalla

Description

This function creates a tidy (i.e. long) table of origin-destination trip data using the Valhalla routing engine. For a set of o origins and d destinations, it returns a tibble with (o x d) rows with the travel distance and time between each pair. It can handle several different travel modes and routing options.

This function is a user-friendly wrapper aroundvalhalla::sources_to_targets(), which calls the Valhalla API directly. sources_to_targets() offers finer- grained control over API options, and so this latter function may be more useful for advanced users.

Notable features of od_matrix():

• You can specify human-readable indices with from_id_col and to_id_col. (Valhalla's API only returns zero-indexed integer identifiers.)

• You can specify a batch_size to break computation into several smaller API calls, to prevent your Valhalla instance from running out of memory. This seems especially important for pedestrian routing, where I've sometimes needed to use a batch size as small as 5.

Usage

od_table(
  froms,
  from_id_col,
  tos,
  to_id_col,
  costing = "auto",
  batch_size = 100,
  minimum_reachability = 500,
  verbose = FALSE,
  hostname = "localhost",
  port = 8002
)

Arguments

froms

A tibble containing origin locations in columns named lat and lon, and an optional column with human-readable names.

from_id_col

The name of the column in froms that contains human-readable names.

tos

A tibble containing destination locations in columns named lat and lon, and an optional column with human-readable names.

to_id_col

The name of the column in tos that contains human-readable names.

costing

The travel costing method: at present "auto", "bicycle", and "pedestrian" are supported.

batch_size

The number of origin points to process per API call.

minimum_reachability

The minimum number of nodes a candidate network needs to have before it is included. Try increasing this value (e.g. to 500) if Valhalla is getting stuck in small disconnected road networks.

verbose

Boolean. Defaults to FALSE. If TRUE, it will provide updates on on the batching process (if applicable).

hostname

Hostname or IP address of your Valhalla instance. Defaults to "localhost".

port

The port your Valhalla instance is monitoring. Defaults to 8002.

Value

A tibble showing the trip distances and times from each origin to each named destination.

Examples

# NOT RUN {
library(dplyr)
library(valhallr)
# set up our inputs
origins <- bind_rows(test_data("parliament"), test_data("uottawa"), test_data("cntower"))
destinations <- bind_rows(test_data("cdntirecentre"), test_data("parliament"))

# generate a tidy origin-destination table
od <- od_table (froms = origins,
                from_id_col = "name",
                tos = destinations,
                to_id_col = "name",
                costing = "auto",
                batch_size = 100,
                minimum_reachability = 500)
# }