R/expand_bounding_box.R

In jfjelstul/eumaps: Tools to make maps of the European Union

# Joshua C. Fjelstul, Ph.D.
# eumaps R package

expand_bounding_box <- function(margin, height, width, bounding_box) {

  bounding_box_ranges <- get_bounding_box_ranges(bounding_box)

  if(!is.null(height)) {
    units_per_px <- bounding_box_ranges$y / height
  } else if(!is.null(width)) {
    units_per_px <- bounding_box_ranges$x / width
  } else {
    stop("Width or height need to be specified.")
  }

  margin_px <- units_per_px * margin

  bounding_box$xmax <- bounding_box$xmax + margin_px
  bounding_box$xmin <- bounding_box$xmin - margin_px
  bounding_box$ymax <- bounding_box$ymax + margin_px
  bounding_box$ymin <- bounding_box$ymin - margin_px

  return(bounding_box)
}