Model 1p permutes the names of the columns of the abundance matrix.
Model 1s permutes the abundances of the categories (columns of the abundance matrix, usually species) within collections (rows of the abundance matrix, usually communities). Only the categories with positive abundances are permuted.
The null models were introduced in Hardy (2008).
Other null model can be used by entering the name of a function. For example, loading the picante
package of R, if model=randomizeMatrix
, then the permutations will follow function randomizeMatrix
available in picante. Any function can be used provided it returns an abundance matrix of similar size as the observed abundance matrix. Parameters of the chosen function can be added to randtest.dpcoa
. For example, using parameter null.model
of randomizeMatrix
, the following command can be used:
randtest.dpcoa(xtest, model = randomizeMatrix, null.model = "trialswap")