spatialEco (version 0.1-5)

tri: Terrain Ruggedness Index

Description

Implementation of the Riley et al (1999) Terrain Ruggedness Index

Usage

tri(r, s = 3, exact = TRUE, file.name = NULL, ...)

Arguments

r

raster class object

s

Scale of window. Must be odd number, can represent 2 dimensions (eg., s=c(3,5) would represent a 3 x 5 window)

exact

Calculate (TRUE/FALSE) the exact TRI or an algebraic approximation.

file.name

Name of output raster (optional)

...

Additional arguments passed to writeRaster

Value

raster class object or raster written to disk

References

Riley, S.J., S.D. DeGloria and R. Elliot (1999) A terrain ruggedness index that quantifies topographic heterogeneity, Intermountain Journal of Sciences 5(1-4):23-27.

Examples

 library(raster)
 r <- raster(nrows=180, ncols=360, xmn=571823.6, xmx=616763.6, ymn=4423540, 
             ymx=4453690, resolution=270, crs = CRS("+proj=utm +zone=12 +datum=NAD83 
             +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"))
   r[] <- runif(ncell(r), 1000, 5000) 
   r <- focal(r, w=matrix(1/121,nrow=11,ncol=11)) 
    
  ( tri.ext <- tri(r) )
  ( tri.app <- tri(r, exact = FALSE) )
  plot(stack(tri.ext, tri.app))