spExtractPoly: Spatial - Extracts point attribute values from...

In FIESTA: Forest Inventory Estimation and Analysis

Spatial - Extracts point attribute values from SpatialPolygons layer(s).

Description

Extracts values from one or more polygon layers and appends to input SpatialPoints layer or data frame. Points are reprojected on-the-fly to projection of SpatialPolygons using PROJ.4 transformation parameters and sf spTransform function.

Usage

spExtractPoly(
  xyplt,
  xyplt_dsn = NULL,
  xy.uniqueid = "PLT_CN",
  polyvlst,
  polyv_dsn = NULL,
  polyvarlst = NULL,
  polyvarnmlst = NULL,
  keepNA = FALSE,
  showext = FALSE,
  savedata = FALSE,
  exportsp = FALSE,
  exportNA = FALSE,
  spMakeSpatial_opts = NULL,
  savedata_opts = NULL,
  gui = FALSE
)

Arguments

xyplt	Data frame object or String. Name of layer with xy coordinates and unique identifier. Can be layer with xy_dsn, full pathname, including extension, or file name (with extension) in xy_dsn folder.
xyplt_dsn	String. Name of database where xyplt is. The dsn varies by driver. See gdal OGR vector formats (https://www.gdal.org/ogr_formats.html).
xy.uniqueid	String.* Unique identifier of xyplt rows.
polyvlst	sf R object or String. Name(s) of polygon layers to extract values. A spatial polygon object, full path to shapefile, or name of a layer within a database.
polyv_dsn	String. Data source name (dsn) where polyvlst layers are found (e.g., *.sqlite, *.gdb, folder name). The dsn varies by driver. See gdal OGR vector formats (https://www.gdal.org/ogr_formats.html).
polyvarlst	String vector or list. The name(s) of variable(s) to extract from polygon(s). If extracting multiple variables from more than one polygon, specify names in a list format, corresponding to polyvlst.
polyvarnmlst	String vector or list. Output name(s) of variable(s) extracted from polygon(s). If extracting multiple variables from more than one polygon, specify names in a list format, corresponding to polyvlst. The number of names must match the number of variables in polyvarlst.
keepNA	Logical. If TRUE, keep NA values.
showext	Logical. If TRUE, layer extents are displayed in plot window.
savedata	Logical. If TRUE, the input data with extracted values are saved to outfolder.
exportsp	Logical. If TRUE, the extracted point data are exported to outfolder.
exportNA	Logical. If TRUE, NULL values are exported to outfolder.
spMakeSpatial_opts	List. See help(spMakeSpatial_options()) for a list of options. Use to convert X/Y values to simple feature (sf) coordinates.
savedata_opts	List. See help(savedata_options()) for a list of options. Only used when savedata = TRUE. If out_layer = NULL, default = 'polyext'.
gui	Logical. If gui, user is prompted for parameters.

Details

*If variable = NULL, then it will prompt user for input.

keepnull
If keepnull=FALSE, points are excluded when all extracted variables from any one SpatialPolygons are NULL, returning the points that fall within the ' intersecting polygons.

Value

pltdat	SpatialPointsDataFrame object or data frame. Input point data with extracted raster values appended. For multi-part polygons, more than 1 row per point may be output.
var.name	String vector. Variable names of extracted variables.

If savedata=TRUE, outdat data frame is saved to outfolder (Default name: datext_'date'.csv). If exportsp=TRUE, the SpatialPointsDataFrame object is exported to outfolder (Default name: datext_'date'.shp). Variable names are truncated to 10 characters or less (See note below). Name changes are output to 'outfn'_newnames_'data'.csv in outfolder.

Note

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

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.

Any names in polygon layers that are the same as in xyplt are renamed to name'_1'.

Author(s)

Tracey S. Frescino

Examples

# Get point data from WYplt data in FIESTA
WYplt <- FIESTA::WYplt

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

# Extract points from polygon vector layer
xyext <- spExtractPoly(xyplt = WYplt,
                       polyvlst = WYbhdistfn,
                       xy.uniqueid = "CN",
                       spMakeSpatial_opts = list(xvar = "LON_PUBLIC",
                                                 yvar = "LAT_PUBLIC",
                                                 xy.crs = 4269))
names(xyext)
xyext$outnames
spxyext <- xyext$spxyext
head(spxyext)
NAlst <- xyext$NAlst

# Plot extracted values of national forest district
plot(spxyext["DISTRICTNU"])

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