R: Centre of Gravity or Mass calculations for spatial data

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 1.1-221.2 Index]