[R] a difficulty in boot package

[Seunghee Baek]

Hi,
I have a problem in programming for bootstrapping.
I don't know why it show the error message.
Please see my code below:
#'st' is my original dataset. 
#functions of 'fml.mlogl','pcopula.fam4','ltd','invltd' are already defined

boot.OR<-function(data,i)
{
E=data[i,]
ml1<-glm(c_VAsex90_bf ~ trt,family=binomial,data=E)
ml2<-glm(c_VAsex90_bm ~ trt,family=binomial,data=E)
marg.covariates<-cbind(rep(1,length(E$trt)),E$trt)
dep.covariates<-cbind(rep(1,length(E$age_avr)),E$age_avr)
start<-c(ml1$coef,ml2$coef,0,0)
fml1<-optim(start,fml.mlogl,control=c(maxit=10000),hessian=F)
x<-(1+exp(fml1$par[1]))^(-1)
y<-(1+exp(fml1$par[3]))^(-1)
b<-exp(fml1$par[5]+fml1$par[6]*43)+1
p00<-ltd(-log(pcopula.fam4(exp(-invltd(x,b)),exp(-invltd(y,b)),b)),b)
p1<-exp(fml1$par[1])/(1+exp(fml1$par[1]))
p2<-exp(fml1$par[3])/(1+exp(fml1$par[3]))
OR<-p00*(p00+p1+p2-1)/(1-p2-p00)/(1-p1-p00)
OR
}

set.seed(101)

boot(st,boot.OR,R=500)

#------------------------------------------------------------#
I gives following error message:
Error in fn(par, ...) : object "dep.covariates" not found

I hope you can help me in this problem.

Thanks,
Becky