spClipRast: Spatial - Subsets a raster to a polygon extent or boundary.

In FIESTA: Forest Inventory Estimation and Analysis

Spatial - Subsets a raster to a polygon extent or boundary.

Description

Subsets a raster to the extent or masked boundary of a spatial polygon object or shapefile (*.shp), with option to write the new file to the outfolder with specified format (fmt).

Usage

spClipRast(
  rast,
  rastfolder = NULL,
  clippolyv,
  clippolyv_dsn = NULL,
  clippolyv.filter = NULL,
  rast.crs = NULL,
  bands = NULL,
  NODATA = NULL,
  buffdist = NULL,
  maskByPolygons = TRUE,
  showext = FALSE,
  fmt = "GTiff",
  compress = FALSE,
  compressType = "DEFLATE",
  outfolder = NULL,
  outfn = "rastclip",
  outfn.pre = NULL,
  outfn.date = FALSE,
  overwrite = FALSE
)

Arguments

rast	String or Raster. Raster name, including extension. Option to include full path.
rastfolder	String. Name of the raster folder. Optional.
clippolyv	SpatialPolygons class R object or String. Name of the polygon spatial layer to use for clipping.
clippolyv_dsn	String. The data source name (dsn; i.e., pathname or database name) of clippolyv. The dsn varies by driver. See gdal OGR vector formats (https://www.gdal.org/ogr_formats.html). Optional if polyv_layer is an R object.
clippolyv.filter	String. Filter to subset clippolyv spatial layer.
rast.crs	EPSG code or PROJ.4 string. Defined coordinate reference system if rast has no crs defined.
bands	Numeric vector. If rast is a multi-layer raster and only 1 or some layers are desired, specify layer number(s) in a vector format. If NULL, all layers are summed.
NODATA	Number. The NODATA value for background values. If NODATA is NULL, and a NODATA value is defined on the input raster, the default is the defined NODATA value, else it is defined based on its datatype (see DEFAULT_NODATA for default data values).
buffdist	Number. The distance to buffer the polygon before clipping raster, in units of raster.
maskByPolygons	Logical. If TRUE, rast is clipped to boundary of polygon. If FALSE, rast is clipped to extent of polygon.
showext	Logical. If TRUE, layer extents are displayed in plot window.
fmt	String. Format for exported raster. Default is format of unput raster. ("raster", "ascii", "SAGA", "IDRISI", "CDF", "GTiff", "ENVI", "EHdr", "HFA", "VRT"). VRT is a virtual raster (See note below).
compress	Logical. If TRUE, compress the final output.
compressType	String. An optional compression type ('LZW', "DEFLATE', "PACKBITS'). Note: If format = 'HFA', a default compression type is used.
outfolder	String. The output folder.
outfn	String. Name of output data file. If NULL, default is 'rastclip'. If no extension, a default is provided to match output format.
outfn.pre	String. Add a prefix to output name (e.g., "01").
outfn.date	Logical. If TRUE, add date to end of outfile (e.g., outfn_'date'.csv).
overwrite	Logical. If TRUE, overwrite files in outfolder.

Details

Use spClipRast() to prompt for input.

If the projection of polyv is different than the projection of rast, the polyv SpatialPolygons object is converted to the projection of rast (See note about on-the-fly projection conversion).

Value

value

Spatial S4 object. A clipped raster file.

The clipped raster is written to outfolder with specified format or same format as input raster.

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.

VRT format Virtual raster format is a pointer to a temporary file, commonly used as an intermediate step between processes. The VRT format ignores option to maskByPolygons.

Author(s)

Tracey S. Frescino

Examples

# Get polygon vector layer from FIESTA external data
WYbhdistfn <- system.file("extdata",
                          "sp_data/WYbighorn_districtbnd.shp", 
                          package = "FIESTA")
WYbhdist <- FIESTA::spImportSpatial(WYbhdistfn)
WYbhdist

# Get raster layers from FIESTA external data
demfn <- system.file("extdata",
                     "sp_data/WYbighorn_dem_250m.img",
                     package = "FIESTA")

# Clip raster to district = '03'
dem03 <- spClipRast(rast = demfn,
                    clippolyv = WYbhdistfn,
                    clippolyv.filter = "DISTRICTNU == '03'",
                    overwrite = TRUE,
                    outfolder = tempdir())
terra::plot(terra::rast(dem03))

# Clip raster to district = '06'
dem06 <- spClipRast(rast = demfn,
                    clippolyv = WYbhdistfn,
                    clippolyv.filter = "DISTRICTNU == '06'",
                    overwrite = TRUE,
                    outfolder = tempdir())

# Plot extracted values of national forest district
terra::plot(terra::rast(dem06))

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