Distance calculations — bng

Compute Euclidean distances between BNG references and distance-based neighbours lists.

Usage

bng_dwithin(bng_ref, d, ...)

bng_distance(bng_ref1, bng_ref2, by_element = FALSE, edge_to_edge = FALSE)

Arguments

bng_ref: object of class BNGReference.
d: numeric. Distance expressed in metres.
...: additional parameters. Not currently used.
bng_ref1, bng_ref2: object of BNGReference
by_element: logical. If TRUE, return a vector with distance between each pair of BNG references. An error is raised if the BNGReference objects are not the same length. Default is FALSE, to return a dense matrix with all pairwise distances.
edge_to_edge: Logical. Should the distances be measured between the edges of the grid references? Default is FALSE to use the centroid.

Value

list containing an unordered vector of BNGReference objects around a given grid square within an absolute distance d.

If by_element is FALSE

bng_distance returns a dense numeric matrix of dimension length(x) by length(y); otherwise it returns a numeric vector the same length as x and y with an error raised if the lengths of x and y are unequal. Distances involving invalid references are NA.

Details

bng_dwithin returns all grids squares for which any part of the boundary is within the distance d of any part of bng_ref's boundary.

Examples

bng_dwithin(as_bng_reference("SU1234"), 1000)
#> [[1]]
#> <BNGReference[9] with Resolution=1km>
#> [1] <SU 11 33> <SU 12 33> <SU 13 33> <SU 11 34> <SU 12 34> <SU 13 34> <SU 11 35>
#> [8] <SU 12 35> <SU 13 35>
#> 

bng_dwithin(as_bng_reference("SU1234"), 1001)
#> [[1]]
#> <BNGReference[21] with Resolution=1km>
#>  [1] <SU 11 32> <SU 12 32> <SU 13 32> <SU 10 33> <SU 11 33> <SU 12 33>
#>  [7] <SU 13 33> <SU 14 33> <SU 10 34> <SU 11 34> <SU 12 34> <SU 13 34>
#> [13] <SU 14 34> <SU 10 35> <SU 11 35> <SU 12 35> <SU 13 35> <SU 14 35>
#> [19] <SU 11 36> <SU 12 36> <SU 13 36>
#> 


ref1 <- as_bng_reference("SE1433")

bng_distance(ref1, as_bng_reference("SE1631"))
#>          [,1]
#> [1,] 2828.427

bng_distance(ref1, as_bng_reference("SENW"))
#>          [,1]
#> [1,] 42807.71

ref2 <- as_bng_reference(c("SE1533", "SE1631", "SE"))
#> Warning: Varying resolutions detected.

bng_distance(ref1, ref2)
#>      [,1]     [,2]     [,3]
#> [1,] 1000 2828.427 39147.16

bng_distance(ref2)
#>           [,1]      [,2]     [,3]
#> [1,]     0.000  2236.068 38242.65
#> [2,]  2236.068     0.000 38268.79
#> [3,] 38242.646 38268.786     0.00

ref3 <- as_bng_reference(c("SE1433", "SE1244"))

bng_distance(ref3, ref2)
#>          [,1]      [,2]     [,3]
#> [1,]  1000.00  2828.427 39147.16
#> [2,] 11401.75 13601.471 37901.19

bng_distance(ref3, ref2[1:2], by_element = TRUE)
#> [1]  1000.00 13601.47

bng_distance(ref1, ref2, edge_to_edge = TRUE)
#>      [,1]     [,2] [,3]
#> [1,]    0 1414.214    0