get_dist_focus {geocausal}

Get distance maps

Description

'get_dist_focus()' generates a distance map from focus locations.

Usage

get_dist_focus(window, lon, lat, resolution, mile = FALSE, preprocess = FALSE)

Arguments

window

owin object

lon

vector of longitudes

lat

vector of latitudes

resolution

resolution of raster objects

mile

logical. 'mile' specifies whether to return the output in miles instead of kilometers (by default, FALSE).

preprocess

logical. 'preprocess' specifies whether to first pick the potentially closest point. It is recommended to set 'preprocess = TRUE' if users need to obtain distances from many points.

Details

'get_dist_focus()' depends on 'geosphere::distVincentyEllipsoid()'. Since it calculates accurate distances considering the ellipsoid, the process sometimes becomes computationally demanding, namely when we need to obtain distances from many points. In that case, users can set 'preprocess = TRUE'. With this option, 'get_dist_focus()' calculates distances from points by first identifying the closest point using 'sf::st_nearest_feature()' with approximations. This process is more efficient than computing distances from all the points with 'geosphere::distVincentyEllipsoid()' and then obtaining the minimum of all the distances. By default, 'get_dist_focus()' returns distances in kilometers unless users set 'mile = TRUE'.

Value

an im object

Examples

get_dist_focus(window = iraq_window,
               lon = c(44.366), #Baghdad
               lat = c(33.315),
               resolution = 0.5,
               mile = FALSE,
               preprocess = FALSE)