get_local_ij {h3jsr}

Get local i, j coordinates

Description

This function defines local i, j coordinates for an H3 destination cell relative to an H3 origin cell.

Usage

get_local_ij(origin = NULL, destination = NULL, simple = TRUE)

Arguments

origin

Character; 15-character cell index generated by H3. A vector of indexes can also be supplied.

destination

Character; 15-character cell index generated by H3. A vector of indexes can also be supplied.

simple

Logical; whether to include an unprojected sfc_POINT geometry column in the output object.

Value

If simple = TRUE, a matrix where each row contains the local i, j coordinates for the supplied destination indexes. If not, an sf object with origin and destination attributes, point geometry of the destination cell centers, and an undefined coordinate reference system.

Note

• The number of indexes supplied to origin and destination must be equal.

• The coordinate space used by this function may have deleted regions or warping due to pentagonal distortion.

• Coordinates are only comparable if they come from the same origin index.

• Failure may occur if the index is too far away from the origin or if the index is on the other side of a pentagon.

• This function is experimental, and its output is not guaranteed to be compatible across different versions of H3.

Examples

# Get local coordinates for a nearby cell
get_local_ij(origin = '86be8d12fffffff', destination = '86be8d127ffffff')

# Get local coordinates for a donut of nearby cells
destinations <- get_ring(h3_address = '86be8d12fffffff', ring_size = 2)
local_coords <- get_local_ij(origin = rep('86be8d12fffffff', length(destinations[[1]])),
                             destination = destinations[[1]],
                             simple = FALSE)

plot(local_coords['destination'], pch = 19) # note origin is (0,0)