2_process.R

# Steps for converting spatial features (sf) objects into SVG land

source("2_process/src/sf_to_coords.R")
source("2_process/src/coords_to_svg_path.R")

p2_targets <- list(
  
  tar_target(svg_width, 1000),
  tar_target(p2_view_bbox, st_bbox(p1_conus_states_sf)),
  
  # Prepare CONUS states for SVG
  
  tar_target(
    p2_conus_states_names,
    p1_conus_states_sf %>% 
      st_drop_geometry() %>% 
      pull(ID)
  ),
  
  tar_target(
    p2_conus_states_coords,
    p1_conus_states_sf %>% 
      filter(ID %in% p2_conus_states_names) %>% 
      sf_to_coords(svg_width, view_bbox = p2_view_bbox),
    pattern = map(p2_conus_states_names)
  ),
  
  tar_target(
    p2_conus_states_paths,
    coords_to_svg_path(p2_conus_states_coords, close_path = TRUE),
    pattern = map(p2_conus_states_coords)
  ),
  
  # Prepare HUCs for SVG
  
  tar_target(
    p2_huc8s_coords,
    sf_to_coords(p1_huc8s_sf[[1]], svg_width, view_bbox = p2_view_bbox),
    pattern = map(p1_huc8s_sf),
    # Keep HUCs in list format so that they can be given unique
    # ids when they are added to the SVG
    iteration = "list"
  ),
  
  tar_target(
    # This will create a vector with one string per polygon
    p2_huc8s_paths,
    coords_to_svg_path(p2_huc8s_coords, close_path = TRUE),
    pattern = map(p2_huc8s_coords)
  ),
  
  # Prepare rivers for SVG
  # TODO: FIX THIS ISSUE
  # Keep getting an error about "could not load dependencies of target
  # p2_river_coords. Input must be a vector, not a <sfc_LINESTRING> object.
  # Doing this fixes that error, which I don't really understand
  tar_target(
    needs_a_solution,
    bind_rows(p1_rivers_sf)
  ),
  tar_target(
    # Returns a list so that each river can be a separate SVG path
    p2_river_coords,
    sf_to_coords_by_id(needs_a_solution, 
                       id_col = "comid",
                       svg_width, 
                       view_bbox = p2_view_bbox),
  ),

  tar_target(
    # This will create a vector with one string per river/comid
    # Using coords_to_svg_path() but with `purrr::map()` bc we 
    # don't need to branch, just need to keep the resulting SVG 
    # paths separate for each river reach. Really fast, so its
    # ok if we rebuild every time new rivers are added.
    p2_river_paths,
    p2_river_coords %>% 
      map(coords_to_svg_path, close_path = FALSE) %>% 
      unlist()
  )
  
)