COGravity: Centre of Gravity or Mass calculations for spatial data

In SDMTools: Species Distribution Modelling Tools: Tools for processing data associated with species distribution modelling exercises

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 [e-mail]

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)

Example output

     COGx   COGx.sd      COGy   COGy.sd      COGz   COGz.sd 
131.97555  12.34252 -32.02445  12.34252 150.05557  28.05119 
    COGx  COGx.sd     COGy  COGy.sd 
33.66667 11.90086 25.50000 14.43468 
    COGx  COGx.sd     COGy  COGy.sd     COGz  COGz.sd 
25.68429 14.14531 25.50000 14.43505 25.68429 14.14531 

SDMTools documentation built on Jan. 11, 2020, 9:23 a.m.