spClipPoly: Spatial - Clip (intersect) polygon vector layer with polygon...

In FIESTA: Forest Inventory Estimation and Analysis

Spatial - Clip (intersect) polygon vector layer with polygon vector layer.

Description

Wrapper for sf::st_intersection, to clip (intersect) polygon vector layer with another polygon vector layer.

Usage

spClipPoly(
  polyv,
  polyv_dsn = NULL,
  clippolyv,
  clippolyv_dsn = NULL,
  clippolyv.filter = NULL,
  showext = FALSE,
  areacalc = FALSE,
  areaunits = "ACRES",
  nolonglat = TRUE,
  exportsp = FALSE,
  savedata_opts = NULL
)

Arguments

polyv	sf R object or String. Polygon data to clip. Can be a spatial polygon object, full pathname to a shapefile, or name of a layer within a database.
polyv_dsn	String. Data source name (dsn; e.g., sqlite or shapefile pathname) of layer to clip. The dsn varies by driver. See gdal OGR vector formats (https://www.gdal.org/ogr_formats.html). Optional if polyv is sf object.
clippolyv	SpatialPolygons class R object or String. Name of the polygon spatial layer to use for clipping.
clippolyv_dsn	String. Data source name (dsn; i.e., pathname or database name) of clippolyv_layer. The dsn varies by driver. See gdal OGR vector formats (https://www.gdal.org/ogr_formats.html). Optional if clippolyv_layer is an R object.
clippolyv.filter	String. Filter to subset clippolyv spatial layer.
showext	Logical. If TRUE, layer extents are displayed in plot window.
areacalc	Logical. If TRUE, calculate area of clipped polygons and append to attribute table (See details).
areaunits	String. If TRUE, calculate area of clipped polygons and append to attribute table ("ACRES", "HECTARES", "SQKM"). If NULL, units of polyv.
nolonglat	Logical. If TRUE, and both layer's coordinate system is long/lat, the layers are converted to a projected CRS before clipping.
exportsp	Logical. If TRUE, the spatial clipped object is exported to outfolder (see spExportSpatial for details).
savedata_opts	List. See help(savedata_options()) for a list of options for saving data. If out_layer = NULL, default = 'polyclip'.

Details

The sf::st_intersection function is used to clip polygons.

areacalc
If areacalc = TRUE and the clipped spatial object is not in a projected coordinate system (i.e., longlat), the object will be reprojected to the Albers Equal Area projection before area is calculated.

Value

sf object of clipped polygon. If polyv and clippolyv have different projections, the projection of returned object will have the same projection as polyv (See note about on-the-fly projection conversion).

If exportsp=TRUE, the sf object will be written to outfolder (See note).

Note

On-the-fly projection conversion
The spTransform (sf) method is used for on-the-fly map projection conversion and datum transformation using PROJ.4 arguments. Datum transformation only occurs if the +datum tag is present in the both the from and to PROJ.4 strings. The +towgs84 tag is used when no datum transformation is needed. PROJ.4 transformations assume NAD83 and WGS84 are identical unless other transformation parameters are specified. Be aware, providing inaccurate or incomplete CRS information may lead to erroneous data shifts when reprojecting. See spTransform help documentation for more details.

ESRI Shapefile Driver
If exportsp=TRUE:
The st_write (sf) function is called. If out_fmt="shp", the ESRI Shapefile driver truncates variable names to 10 characters or less. Variable names are changed before export using an internal function (trunc10shp). If sf object has more than 1 record, it will be returned but not exported.

Author(s)

Tracey S. Frescino

Examples

## Not run: 
# Load in USAco data from geodata package
USAco <- geodata::gadm(country="United States", level=2, path=tempdir())

# Set up data from FIESTA
WYbhfn <- system.file("extdata", "sp_data/WYbighorn_adminbnd.shp",
                                    package = "FIESTA"))

# Clip polygon with WY Bighorn object from FIESTA
WYbhco <- spClipPoly(polyv = USAco,
                     clippolyv = WYbhfn)     

## End(Not run)

FIESTA documentation built on Nov. 22, 2023, 1:07 a.m.