hexgridd.r

getHexGrid <- function(spdf, cellsize){
  boundingBox <- bbox(spdf)

  boundingBox[1,1] <- boundingBox[1,1] - cellsize
  boundingBox[2,1] <- boundingBox[2,1] - cellsize
  boundingBox[2,2] <- boundingBox[2,2] + cellsize
  cols = ceiling(((boundingBox[1,2] - boundingBox[1,1]) + 3 * cellsize) / cellsize)
  rows = ceiling((boundingBox[2,2] - boundingBox[2,1]) / cellsize)
 
  x_left_origin = boundingBox[1,1]
  y_bottom_origin = boundingBox[2,1]
 
  xvertexlo = 0.288675134594813 * cellsize
  xvertexhi = 0.577350269189626 * cellsize
  x_spacing = xvertexlo + xvertexhi
 
  output <- ""
  for(col in seq(cols+1)){
    x1 = x_left_origin + (col * x_spacing)
    x2 = x1 + (xvertexhi - xvertexlo)
    x3 = x_left_origin + ((col + 1) * x_spacing)
    x4 = x3 + (xvertexhi - xvertexlo)
    for(row in seq(rows+1)){
              t = col %% 2
              y1 = y_bottom_origin + (((row * 2) + t) * (cellsize / 2))
              y2 = y_bottom_origin + (((row * 2) + t+1) * (cellsize / 2))
              y3 = y_bottom_origin + (((row * 2) + t+2) * (cellsize / 2))
      output <- paste0(output, "POLYGON((",
                       x1," ",y2 , ",", x2, " ", y1, ",", x3, " ", y1, ",",
                       x4, " ", y2, ",", x3, " ", y3, ",", x2, " ", y3, ",", x1, " ", y2, ")),")
    }
  }
  spPoly <- rgeos::readWKT(paste0("GEOMETRYCOLLECTION(", substr(output, 1, nchar(output)-1), ")"))
  return(SpatialPolygonsDataFrame(Sr = spPoly,
                                  data = data.frame("id" = getSpPPolygonsIDSlots(spPoly))))
}