artificial.data: Create an artificial data set

Description Usage Arguments Details Value Authors Examples

Description

artificial.data creates an artifical data set of multispecies presence absence data based on a binomial response

Usage

1
artificial.data(formula,data,theta,S,dist="bernoulli")

Arguments

formula

an object of class "formula" (or one that can be coerced to that class):a symbolic description of the model to be fitted

data

a data frame containing the variables in the formula

theta

coefficents for each species archetype. Matrix of G x number of parameters. Each row is a different species archetype.

S

number of species to create

dist

The distribution to sample from, "bernoulli" gives presence/absence (default), "negbin" gives abundances. For negbin, intercepts are chosen at random from -5 to 5, theta held at 1.

Details

each species is a random realisation of the archetype species

Value

a list with elements pa (matrix of presence absence data) and group (membership of each species to each group)

Authors

Piers Dunstan and Scott Foster

Examples

1
2
3
4
5
6
7
8
## for bernoulli
theta <- matrix(c(-0.9,-0.6,0.5,1,-0.9,1,0.9,-0.9),4,2,byrow=TRUE)
dat <- data.frame(y=rep(1,100),x=runif(100,0,2.5))
dat1 <- artificial.data(y~1+x,dat,theta,20)
## for negbin
theta <- matrix(c(-0.9,-0.6,0.5,1,-0.9,1,0.9,-0.9),4,2,byrow=TRUE)
dat <- data.frame(y=rep(1,100),x=runif(100,0,2.5))
dat1 <- artificial.data(y~1+x,dat,theta,20,dist="negbin")

SpeciesMix documentation built on May 29, 2017, 5:47 p.m.