nlm_mpd: nlm_mpd
In NLMR: Simulating Neutral Landscape Models

Description Usage Arguments Details Value References Examples

Simulates a midpoint displacement neutral landscape model.

nlm_mpd(
  ncol,
  nrow,
  resolution = 1,
  roughness = 0.5,
  rand_dev = 1,
  torus = FALSE,
  rescale = TRUE,
  verbose = TRUE
)

`ncol`	[`numerical(1)`] Number of columns forming the raster.
`nrow`	[`numerical(1)`] Number of rows forming the raster.
`resolution`	[`numerical(1)`] Resolution of the raster.
`roughness`	[`numerical(1)`] Controls the level of spatial autocorrelation (!= Hurst exponent)
`rand_dev`	[`numerical(1)`] Initial standard deviation for the displacement step (default == 1), sets the scale of the overall variance in the resulting landscape.
`torus`	[`logical(1)`] Logical value indicating wether the algorithm should be simulated on a torus (default FALSE)
`rescale`	[`logical(1)`] If `TRUE` (default), the values are rescaled between 0-1.
`verbose`	[`logical(1)`] If `TRUE` (default), the user gets a warning that the functions changes the dimensions to an appropriate one for the algorithm.

The algorithm is a direct implementation of the midpoint displacement algorithm. It performs the following steps:

Initialization: Determine the smallest fit of max(ncol, nrow) in n^2 + 1 and assign value to n. Setup matrix of size (n^2 + 1)*(n^2 + 1). Afterwards, assign a random value to the four corners of the matrix.
Diamond Step: For each square in the matrix, assign the average of the four corner points plus a random value to the midpoint of that square.
Diamond Step: For each diamond in the matrix, assign the average of the four corner points plus a random value to the midpoint of that diamond.

At each iteration the roughness, an approximation to common Hurst exponent, is reduced.

RasterLayer

https://en.wikipedia.org/wiki/Diamond-square_algorithm

# simulate midpoint displacement
midpoint_displacememt <- nlm_mpd(ncol = 100,
                                 nrow = 100,
                                 roughness = 0.3)
## Not run: 
# visualize the NLM
landscapetools::show_landscape(midpoint_displacememt)

## End(Not run)