error in ZIGP package and optim

Dear all: I am trying to use the response.zigp and est.zigp from the ZIGP
package. Firstly, I generated a simple data via response.zigp and then I try
to fit them by est.zigp function, this is the code:
---------------------------------

library(ZIGP)
#try-ZIGP-1
n<-100
X<-matrix(c(rep(1,n),runif(n*2,0,1)),n,3)
W<-matrix(c(rep(1,n),rbinom(n,1,0.5)),n,2)
Z<-matrix(c(rep(1,n),rbinom(n,1,0.5)),n,2)
beta<-c(1,-2,1)
alpha<-c(1,1.5)
gamma<-c(-1,2)
y<-response.zigp(X,W,Z,beta,alpha,gamma)
x1<-as.vector(X[,1])
x2<-as.vector(X[,2])
x3<-as.vector(X[,3])
w1<-as.vector(W[,1])
w2<-as.vector(W[,2])
z1<-as.vector(Z[,1])
z2<-as.vector(Z[,2])
fm.X<-~x1+x2+x3
fm.W<-~1
fm.Z<-~z1+z2
est.zigp(y,fm.X,fm.W,fm.Z,Offset=rep(1,length(y)),init=FALSE)

-----------------------------
Then I get the *error:*
----------------------------
Error in optim(par = start.delta, fn = loglikelihood.zigp, gr = gradient,  : 
  initial value in 'vmmin' is not finite
--------------------------------
Any help you can give me would be greatly appreciated.


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