extract.data: Spatial Join of Points with Raster Grids

Description Usage Arguments Details Value Author(s) Examples

View source: R/extract.data.R

Description

extract.data extracts data from raster object of class 'asc' (this and the adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package) at specified locations. This represents a faster version of 'join.asc' of the adehabitat package that assumes all locations are within the map extents.

Note: there is no interpolation done here. The values reported are simply the values of the raster cell the point falls into.

Usage

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## S3 method for class 'data'
extract(pts, x)

Arguments

pts

a two-column data frame or matrix with the x and y coordinates of the locations of interest.

x

a raster matrix of class 'asc' (this and the adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package)

Details

Implements a faster version of 'join.asc' from the adehabitat package.

NOTE: this assumes all locations are within the extent of the raster map. Values outside the extent will be given a value of NA.

Value

Returns a vector equal in length to the number of locations in pnts.

Author(s)

Jeremy VanDerWal jjvanderwal@gmail.com

Examples

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#create a simple object of class 'asc'
tasc = as.asc(matrix(1:50,nr=50,nc=50)); print(tasc)

#define some point locations
points = data.frame(x=runif(25,1,50),y=runif(25,1,50))

#extract the data
points$values = extract.data(points,tasc)

#show the data
print(points)

SDMTools documentation built on May 30, 2017, 1:21 a.m.

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