R problem with finding all combinations of coordinates in a hexagonal grid-CodePudding

Given the coordinates of any hexagon in the image below, I want to return the 6 sets coordinates of the adjacent hexagons. What is the best approach to this? I have figured out that the coordinates adjacent to (x,y) consist of all combinations of x-1,x,x 1,y-1,y,y 1 but I'm not sure the best way to approach this programmatically.

CodePudding user response：

The coordinates adjacent to (x,y) are not all combinations of those expressions because there are 9 such combinations and only 6 adjacent hexes ((1, 1), (-1, -1) and (0, 0) are not adjacent to (0, 0)).

An R function to list the correct coords needn't be any more complicated than this:

adjacent_coords = function(x) {
  list(c(x[1], x[2] 1),
       c(x[1] 1, x[2]),
       c(x[1] 1, x[2]-1),
       c(x[1], x[2]-1),
       c(x[1]-1, x[2]),
       c(x[1]-1, x[2] 1))
}

adjacent_coords(c(1, -1))
[[1]]
[1] 1 0

[[2]]
[1]  2 -1

[[3]]
[1]  2 -2

[[4]]
[1]  1 -2

[[5]]
[1]  0 -1

[[6]]
[1] 0 0

CodePudding user response：

something like this?

library(tibble)
neighbours <- function(x,y) {
  center <- c(x,y)
  n1 <- c(x, y   1)
  n2 <- c(x   1, y)
  n3 <- c(x   1, y - 1)
  n4 <- c(x, y - 1)
  n5 <- c(x - 1, y)
  n6 <- c(x - 1, y   1)
  return(tibble::lst(center, n1, n2, n3, n4, n5, n6))
}

neighbours(1,1)

$center
[1] 1 1

$n1
[1] 1 2

$n2
[1] 2 1

$n3
[1] 2 0

$n4
[1] 1 0

$n5
[1] 0 1

$n6
[1] 0 2