optimized.run {ZIGP}R Documentation

Calculation of valid initial values

Description

'optimized.run' calculates valid initial values for the 'optim' method.

Usage

optimized.run(Y, X, W, Z)

Arguments

Y response vector of length n.
X design matrix of dim (n x p) for mean modelling.
W design matrix of dim (n x r) for overdispersion modelling.
Z design matrix of dim (n x q) for zero inflation modelling.

Details

t.i has to be defined as the exposure. n has to be defined as the number of observations dim(X)[1].

Examples

Y <- c(3,0,2)
X <- matrix(c(1:3,4,3,5),3,2)
W <- c(3,-4,-1)
Z <- rep(1,3)
n <- dim(X)[1]
t.i <<- rep(1,n)
optimized.run(Y,X,W,Z)
#[1]           X1         X2          W          Z 
#[2]   -0.6783368  0.4559966  0.1238029 -1.3862944 

## The function is currently defined as
function(Y,X,W,Z)

{


# improved initial values

# get initial beta, phi & omega

  out <- mle.zigp.full.like(Y, X, Offset = t.i, summary=FALSE)

  beta.start <- out$Coefficients

  phi.first <- out$Dispersion.Parameter

  omega.first <- out$ZI.Parameter


# LM for alpha

  rechte.seite <- rep(log(phi.first - 1),n)

  out<-lm(rechte.seite ~ W-1)

  alpha.start <- out$coefficients


# LM for gamma

  rechte.seite <- rep(log(omega.first)-log(1-omega.first),n)

  out<-lm(rechte.seite ~ Z-1)

  gamma.start <- out$coefficients

  rm(rechte.seite,out)


  start.delta <- c(beta.start,alpha.start,gamma.start)

  rm(beta.start,alpha.start,gamma.start)


  return(start.delta)

  }

[Package ZIGP version 1.3 Index]