Topographic Position Index (tpi)

Calculates topographic position using mean deviations

tpi(x, scale = 3, win = "rectangle", normalize = FALSE, zero.correct = FALSE)

Arguments

x	A raster class object
scale	focal window size (n-cell x n-cell for rectangle or distance for circle)
win	Window type. Options are "rectangle" and "circle"
normalize	Apply deviation correction that normalizes to local surface roughness
zero.correct	Apply correction for zero values in matrix weights

Value

raster class object of tpi metric

References

De Reu, J., J. Bourgeois, M. Bats, A. Zwertvaegher, V. Gelorini, et al., (2014) Application of the topographic position index to heterogeneous landscapes. Geomorphology, 186:39-49.

Author

Jeffrey S. Evans <jeffrey_evans@tnc.org>

Examples

# \donttest{
 library(raster)
 data(elev)

# calculate tpi and plot 
  tpi7 <- tpi(elev, scale=7) 
  tpi025 <- tpi(elev, win = "circle", scale=0.025)
#> Error in tpi(elev, win = "circle", scale = 0.025): Scale is too small for a circular window
  tpi025.zc <- tpi(elev, win = "circle", scale=0.025, 
                   zero.correct = TRUE)
#> Error in tpi(elev, win = "circle", scale = 0.025, zero.correct = TRUE): Scale is too small for a circular window

opar <- par(no.readonly=TRUE)
    par(mfrow=c(2,2))
      plot(elev, main="original raster")
      plot(tpi7, main="tpi 7x7")
      plot(tpi025, main="tpi Circular window d=0.025")
#> Error in h(simpleError(msg, call)): error in evaluating the argument 'x' in selecting a method for function 'plot': object 'tpi025' not found
   plot(tpi025, main="tpi Circular window d=0.025, zero correct")
#> Error in h(simpleError(msg, call)): error in evaluating the argument 'x' in selecting a method for function 'plot': object 'tpi025' not found
par(opar)
# }