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Get a bounding box buffered a set distance or to match an aspect ratio

Source: R/st_bbox_ext.R
st_bbox_ext.Rd

st_bbox_ext() converts the input to a bounding box with as_bbox(), applies a buffer (based on a specified distance or proportion of the diagonal distance across the bounding box) and adjusts the bounding box aspect ratio before returning a bounding box (or another class specified by the class parameter). If the input object is a list or sf_list object, the function always returns a list or sf_list.

Usage

st_bbox_ext(
  x,
  dist = NULL,
  diag_ratio = NULL,
  asp = NULL,
  unit = NULL,
  crs = NULL,
  class = "bbox",
  nudge = NULL,
  allow_null = TRUE,
  allow_list = TRUE
)

st_bbox_asp(
  x,
  asp = NULL,
  class = "bbox",
  allow_null = TRUE,
  allow_list = TRUE
)

Arguments

x

A sf, sfc, bbox, sfg, Raster, Spatial, Extent, numeric, or character object (a place name passed to osmdata::getbb()). See as_bbox() for more details.

dist

buffer distance in units. Optional.

diag_ratio

ratio of diagonal distance of area's bounding box used as buffer distance. e.g. if the diagonal distance is 3000 meters and the "diag_ratio = 0.1" a 300 meter will be used. Ignored when dist is provided.

asp

Aspect ratio of width to height as a numeric value (e.g. 0.33) or character (e.g. "1:3"). If numeric, get_asp() returns the same value without modification.

unit

Units for buffer. Supported options include "meter", "foot", "kilometer", and "mile", "nautical mile" Common abbreviations (e.g. "km" instead of "kilometer") are also supported. Distance in units is converted to units matching GDAL units for x; defaults to "meter"

crs

Coordinate reference system of bounding box to return; defaults to NULL which maintains the crs of the input object.

class

Class of object to return passed to as_sf_class(); defaults to "bbox".

nudge

Passed as to parameter st_nudge() when not NULL. A numeric vector, a sf object, or any other object that can be converted to a simple feature collection with as_sfc()..

allow_null

If TRUE (default) and x is NULL, return NULL or, if FALSE, abort function.

allow_list

If TRUE (default), allow sf list objects as an input and use purrr::map() to apply the provided parameters to each object within the list to return as a new sf list object.

Value

A bbox object converted to match the class of the class parameter.

Details

st_bbox_asp() supports aspect ratio adjustments without applying a buffer. asp can be supplied as a number or a string matching the format of "width:height". Common aspect ratios include "1:1" (1), "4:6" (0.666), "8.5:11", "16:9" (1.777).