addWalkingPath {cholera}

Add the shortest walking path between a selected cases or pumps.

Description

Add the shortest walking path between a selected cases or pumps.

Usage

addWalkingPath(origin = 1, destination = NULL, type = "case-pump",
  observed = TRUE, weighted = TRUE, vestry = FALSE,
  distance.unit = "meter", time.unit = "second", walking.speed = 5,
  unit.posts = "distance", unit.interval = NULL, alpha.level = 1)

Arguments

origin

Numeric or Integer. Numeric ID of case or pump.

destination

Numeric or Integer. Numeric ID(s) of case(s) or pump(s). Exclusion is possible via negative selection (e.g., -7). Default is NULL: this returns closest pump or "anchor" case. Character landmark name (case insensitive).

type

Character "case-pump", "cases" or "pumps".

observed

Logical. Use observed or "simulated" expected data.

weighted

Logical. TRUE computes shortest path in terms of road length. FALSE computes shortest path in terms of nodes.

vestry

Logical. TRUE uses the 14 pumps from the Vestry Report. FALSE uses the 13 in the original map.

distance.unit

Character. Unit of distance: "meter", "yard" or "native". "native" returns the map's native scale. unit is meaningful only when "weighted" is TRUE. See vignette("roads") for information on unit distances.

time.unit

Character. "hour", "minute", or "second".

walking.speed

Numeric. Walking speed in km/hr.

unit.posts

Character. "distance" for mileposts; "time" for timeposts.

unit.interval

Numeric. Sets interval between posts: for "distance", the default is 50 meters; for "time", the default is 60 seconds.

alpha.level

Numeric. Alpha level transparency for path: a value in [0, 1].

Value

An R list with two elements: a character vector of path nodes and a data frame summary.

Note

The function uses a case's "address" (i.e., a stack's "anchor" case) to compute distance. Time is computed using cholera::distanceTime(). Adam and Eve Court, and Falconberg Court and Falconberg Mews, are disconnected from the larger road network; they form two isolated subgraphs. This has two consequences: first, only cases on Adam and Eve Court can reach pump 2 and those cases cannot reach any other pump; second, cases on Falconberg Court and Mews cannot reach any pump. Unreachable pumps will return distances of Inf. Arrow points represent mileposts or timeposts to the destination.

Examples

streetNameLocator("broad street", zoom = TRUE, highlight = FALSE,
  add.subtitle = FALSE)
addWalkingPath(447)