I have data in the form given below, and I want to perform forecasting using multiple regression. I found definition of multiple regression from this link: http://otexts.com/fpp/5/1/ . I have these questions: (1) Can we forecast value of Y (the dependent variable) based on the given values of the independent variables (X1 and X2), as in below table? or it is mandatory to have previous values of Y along with X1 and X2 to forecast the future value of Y, (2) I want to forecast the value of Y at T8, by providing two inputs, i.e., value of Y_at_T8 = forecast(X1=22, X2=33), how to proceed on that? , (3) Is it mandatory for multiple regression that Time must be in fixed intervals, can it increase in varying intervals?