R/older-functions/make-grid.R

In pbs-assess/PACea: An R package of Pacific ecosystem information to help facilitate an ecosystem approach to fisheries management

##' Make the master grid
##'
##' Internal function for developers, to create the master grid. Andy
##' functionalised from Joe's original code. Function will need
##' changing/adapting/deprecating if we use a new coastline object. And if we
##' decide on a non-regular grid - coarser away from the coast.
##'
##' @param coastline `SpatialPolygons` object (from `sp` package) to represent
##'   the coastline. Probably only works for `Coastline` for now, which Joe got
##'   from somewhere.
##' @param cell_size_x size of each cell in the (pseudo, due to rotation) x
##'   direction, km
##' @param cell_size_y size of each cell in the (pseudo, due to rotation) y
##'   direction, km
##' @param rotang angle to rotate the grid
##' @return a grid to use as a master grid, of class `sf` and `data.frame`
##' @author Andrew Edwards
##' @examples
##' \dontrun{
##' # See data-raw/grids/test-grids.R
##' }
make_grid <- function(coastline,
                      cell_size_x = 2,
                      cell_size_y = 2,
                      rotang = 318.5){
# DECIDE WHICH TO INCLUDE AS DEFAULT, num or cell size

  # create large pixel grid over the simplified coastline
  # Rotate the grid to maximize the spatial overlap

  center <- sf::st_centroid(sf::st_union(coastline))

  # This is the function call which actually creates the master grid
  # To increase the resolution (almost certainly desired), increase the
  # n argument (e.g. n=c(100,100)) or reduce the cellsize (which seems more
  # intuitive, it should be each direction in km's.

  Coastline_Grid <- sf::st_sf(
                          sf::st_make_grid(tran(sf::st_geometry(coastline),
                                                -rotang,
                                                center),
                                           cellsize = c(cell_size_x,
                                                        cell_size_y)))

# Have this option for numbers of cells, though am thinking cell_size is more intuitive
#  Coastline_Grid <- sf::st_sf(
#                          sf::st_make_grid(tran(sf::st_geometry(Coastline),
#                                                -rotang, center),
#                                           n=c(10,10)))

  Coastline_Grid <- tran(sf::st_geometry(Coastline_Grid),
                         rotang,
                         center)

  # May need the bit from Create_BC_Partition_New.Rmd that adds the extra
  # 50km. Can do that in here, just the once, and then presumably save
  # it. Waiting to see where Joe said he got Coastline.rda from.

  # Keep only the polygons that fall within or touch the original Coastline to save storage space
  Coastline_Grid <- sf::st_as_sf(sf::as_Spatial(Coastline_Grid))
  sf::st_crs(Coastline_Grid) <- sf::st_crs(coastline)

  # Name the individual polygons by row-column method
  # Note that sf works from bottom-left to top-right
  # The first grid cell is the bottom-left grid cell (1,1)
  # The final grid cell is the top-right grid cell (n,n)
  # NEED TO CHANGE THE VALUES 10 TO MATCH THE CHOICE OF n=c(,) above!!
# Only currently works for cell_size_x = cell_size_y = 20
#  Coastline_Grid$Poly_Name <- paste0('Grid_Index_(',
#                                     rep(1:17, each = 53), # repeat each value of 1:cols, nrows
#                                     ',',
#                                     rep(1:53, times = 17), # repeat sequence 1:nrows, ncols times
#                                    ')')
# Don't get how that works given we've taken some out. BUT I don't think we want
# to do the fancy x,y labelling. That will all be behind the scenes, and it's
# just as simple to have a single number. Think someone suggested the x,y
# format, probably thinking the user would see that more (also before we thought
# about much higher resolution).

  # This gets rid of the un-needed cells (AE: I don't understand how though)
  Coastline_Grid  <- Coastline_Grid[Coastline, ]

  # Number each cell 1, 2, 3, ...
  Coastline_Grid <- Coastline_Grid %>%
    dplyr::mutate(id = row_number())

  Coastline_Grid
}