COGravity {SDMTools}R Documentation

Centre of Gravity or Mass calculations for spatial data

Description

COGravity calculates the Centre of Gravity (or also known as Centre of Mass) for point or raster spatial data.

Note: NA data is automatically ommitted from analysis.

Usage

COGravity(x, y = NULL, z = NULL, wt = NULL)

Arguments

x

a vector of e.g., longitudes or eastings, or a raster of class 'asc', 'RasterLayer' or 'SpatialGridDataFrame'.

y

a vector of e.g., latitudes or northings.

z

a vector of e.g., elevations.

wt

a vector or raster of class 'asc', 'RasterLayer' or 'SpatialGridDataFrame' representing weights for data.

Details

For raster-based data, if wt is missing, the values of the ascii are assumed to be the weights; otherwise, the values are assumed to be the z values.

Value

Returns a named vector of data representing the Centre of Gravity in x, y & z dimensions (depending on data supplied).

Author(s)

Jeremy VanDerWal jjvanderwal@gmail.com

Examples

#create some points
x = seq(154,110,length=25)
y = seq(-10,-54,length=25)
z = seq(100,200,length=25)
wt = runif(25) #random weights
#calculate the Centre of Gravity for these points
COGravity(x,y,z,wt)

#create a simple objects of class 'asc'
x = as.asc(matrix(1:50,nr=50,nc=50))
wt = as.asc(matrix(runif(50),nr=50,nc=50))

#calculate COG with weighting defined in x
COGravity(x)
#calculate COG with weighting defined in wt (values in x are assumed elevation (z))
COGravity(x,wt=wt)

[Package SDMTools version 1.1-221 Index]