landsepi (version 0.0.8)

multiN: Allocation of cultivars

Description

Algorithm based on latent Gaussian fields to allocate two different types of crops across the simulated landscapes.

Usage

multiN(d, area, range, prop)

Arguments

d

a matrix of the pairwise distances between the centroids of the fields of the landscape.

area

vector containing the areas of the fields.

range

range of spatial autocorrelation between fields (<0 for fragmented landscapes, >0 for aggregated landscapes, =0 for random allocation).

prop

relative proportion of the second type of crop.

Value

A dataframe containing the index of each field (column 1) and the index (0 or 1) of the type of crop grown on these fields (column 2).

Details

This algorithm allows the control of the proportions of each type of crop in terms of surface coverage, and their level of spatial aggregation. A random vector of values is drawn from a multivariate normal distribution with expectation 0 and a variance-covariance matrix which depends on the pairwise distances between the centroids of the fields. The variance-covariance matrix is computed from a periodic function for highly fragmented or highly aggregated types of crops, an exponential function for moderately aggregated types of crops, and from a normal distribution for a random allocation of the types of crops. Next, the two types of crops are allocated to different fields depending on whether the each value drawn from the multivariate normal distribution is above or below a threshold. The proportion of each type of crop in the landscape is controlled by the value of this threshold (parameter prop).

Examples

# NOT RUN {
d <- matrix(rpois(100,100), nrow=10)
area <- data.frame(num=1:10, area=10)
## Fragmented landscape
multiN(d, area, range=-2, prop=0.5)
# }