R/gPolyByIntersect2.R

In WCS-Marine/local-reef-pressures: Analysis of local human pressures on tropical coral reefs

gPolyByIntersect2 <- function(container, reference, threshold = 0, centroid = F) {
  # From mSpatial::gPolyByIntersect
  # container <- tile_pol
  # reference <- allreefs_buffer
  # threshold = 0
  # centroid = T

  if (centroid) {
    centroids <- gCentroid(reference, byid = T)
    ta_blocks_bbox_centroids_idx <- gWhichPoints(
      centroids,
      bbox(container)
    )
    if (length(ta_blocks_bbox_centroids_idx) == 0) {
      return(NULL)
    } ### Added this line to avoid error when the intersection is empty
    ta_blocks_bbox <- reference[ta_blocks_bbox_centroids_idx, ]
    ta_blocks_bbox[which(gContains(container, gCentroid(ta_blocks_bbox,
      byid = T
    ), byid = T)), ]
  }
  else {
    slivers <- raster::intersect(reference, container)
    sliver.area <- gArea(spTransform(slivers, CRS("+init=epsg:3857")),
      byid = T
    )
    reference.area <- gArea(spTransform(reference[slivers, ], CRS("+init=epsg:3857")), byid = T)
    overlap <- sliver.area / reference.area
    reference[slivers, ][which(overlap > threshold), ]
  }
}