Dear R People: I know that we can use arima in the following fashion: arima(x,order=c(7,0,0),include.mean=FALSE,fixed=c(NA,rep(0,5),NA)) and that works fine. My question is: does the ar function work in the same way, please? I've tried a few things, but they don't seem to work. Thanks, Erin PS the arima will do, but I was just double checking. -- Erin Hodgess Associate Professor Department of Computer and Mathematical Sciences University of Houston - Downtown mailto: erinm.hodgess at gmail.com