extract: Extracts values at points from a list of files

In GSIF: Global Soil Information Facilities

Description

Overlays and extracts values at points from a list of raster layers defined as file names (e.g. GeoTiffs). Extends the extract function from the raster package. Especially suitable for extracting values of a large list of rasters that have not been organized into a mosaick (a virtual stack), for example a list of Landsat scenes.

Usage

## S4 method for signature 'SpatialPoints,character'
extract(x, y, 
   path=".", ID = "SOURCEID", 
   method = "simple", is.pattern = FALSE, force.projection = TRUE, 
   NAflag = "", show.progress=TRUE, isFactor=FALSE, ...)
## S4 method for signature 'SpatialPointsDataFrame,character'
extract(x, y, 
   path = ".", ID = "SOURCEID", 
   method = "simple", is.pattern = FALSE, force.projection = TRUE, 
   NAflag = "", show.progress=TRUE, isFactor=FALSE, ...)

Arguments

x	object of class "SpatialPoints*"
y	character; list of files that can be read using the raster function
path	optional working directory where the files are stored
ID	character; column name for the unique identifier (if object is of class "SpatialPoints" "SOURCEID" column is automatically generated)
method	character; resampling method (see raster::extract)
is.pattern	logical; specifies whether the list is a pattern
force.projection	logical; specifies whether the reprojection should be ignored
NAflag	character; missing value flag (all missing values are removed by default)
show.progress	logical; specifies whether to display the progress bar
isFactor	logical; turns aggregation on off for factor type variable
...	additional arguments that can be passed to the raster::extract function

Note

The method will try to reproject the values to the native coordinate system, hence it is highly advisible to embed the proj4 string into the GeoTiffs. If both x and y are in the same coordinate system, then reprojection can be turned off by setting force.projection = FALSE. In the case is.pattern = TRUE (search by pattern), missing values are removed by default and if multiple rasters covering the same area are found, values are aggregated to the mean value.

Author(s)

Tomislav Hengl

See Also

raster::extract, warp

GSIF documentation built on May 2, 2019, 5:44 p.m.