R: Spatial Join of Points with Raster Grids

extract.data {SDMTools} | R Documentation

## Spatial Join of Points with Raster Grids

### 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

    ## 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

    #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)

[Package SDMTools version 1.1-221.2 Index]