[R] Estimate Intercept in ARIMA model

[doublelin15]

Hi, All,
   This is my program

ts1.sim <- arima.sim(list(order = c(1,1,0), ar = c(0.7)), n = 200)
ts2.sim <- arima.sim(list(order = c(1,1,0), ar = c(0.5)), n = 200)
tdata<-ts(c(ts1.sim[-1],ts2.sim[-1]))
tre<-c(rep(0,200),rep(1,200))
gender<-rbinom(400,1,.5)
x<-matrix(0,2,400)
x[1,]<-tre
x[2,]<-gender
fit <- arima(tdata, c(1, 1, 0), method = "CSS",xreg=t(x))

   I try to fit a ARIMA model and aclude some other independent 
variable in this model, but why the outcome does not have the
intercept estimate value? and if the model is arima(tdata, c(p, 0, q)
there will have this value, why have this difference? 

   And if i want analysis Interrupted time series, what can i do?
I find urca can help you to find the interrupted point, but if I
already know this point, and want to compare the mean, level and 
slope, any package can help me to do this?


Thanks for your attention!
                                              

-- 
MingChuanUniversity 
Department of Applied Statistic and Information Science
YuJr Lin 

Tel:03-3281200#8881 
E-mail:doublelin15 at adm.cgmh.org.tw