想建立自回归模型，对一阶、三阶、十二阶进行回归

m12=arima(x,order=c(12,0,0)，fixed=c(NA,0,NA,0,0,0,0,NA,0,0,0,NA))
错误: unexpected symbol in "m12=arima(x,order=c(12,0,0)fixed"

应该怎么做呢？？？请大家帮帮忙