Functions and code to create a hexagonal grid.

hexagonal-grid.R

# Cannot remember the source for this code, it isn't mine. 


genHexGrid <- function(dx, ll = c(0, 0), ur = c(1, 1))
{
    dy <- sqrt(3) * dx / 2
    
    x <- seq(ll[1], ur[1] - dx / 2, dx)
    y <- seq(ll[2], ur[2], dy)
    
    y <- rep(y, each = length(x))
    x <- rep(c(x, x + dx / 2), length.out = length(y))
    
    x <- x + (ur[1] - max(x)) / 2
    y <- y + (ur[2] - max(y)) / 2
    
    list(x = x, y = y)
}

genPolyList <- function(hexGrid)
{
    dx <- hexGrid$x[2] - hexGrid$x[1]
    dy <- dx / sqrt(3)
    
    x.offset <- c(-dx / 2, 0, dx / 2, dx / 2, 0, -dx / 2)
    y.offset <- c(dy / 2, dy, dy / 2, -dy / 2, -dy, -dy / 2)
    
    f <- function(i) list(x = hexGrid$x[i] + x.offset,
                          y = hexGrid$y[i] + y.offset)
    
    lapply(1:length(hexGrid$x), f)
}

xy <- genHexGrid(0.05)
plot(xy, asp = 1, axes = F, pch = 19, xlab = NA, ylab = NA, cex = 0.5)
lapply(genPolyList(xy), polygon, xpd = NA, ypd = NA)