I am new to R and new to time series modeling. I have a set of variables (var1, var2, var3, var4, var5) for which I have historical yearly data. I am trying to use this data to produce a prediction of var1, 3 years into the future.
I have a few basic questions: 1) I am able to read in my data, and convert it to a time series format using 'ts.' data_ts <- ts(data, start = 1988, end = 2005, frequency = 1, deltat = 1) However, I am not able to refer to the individual columns or variables of my new time series object. For example, I am able to reference 'var1' by typing, data$var1, but I can not do the same by using data_ts$var1. I don't see how I can use data_ts without being able to reference the individual columns in my dataset. 2) Since I'm trying to build a multivariate time series model, I want to find the correlations of var1 with my other variables (var1, var2, ...etc.) and their lagged values. But since I'm trying to produce a forecast for 3 years into the future, I want to find the ccf between var1 and my other variables lagged 3 years. I tried doing: ccf(var1, lag(var2, 3)) but I get the following error: Error in na.fail.default(ts.union(as.ts(x), as.ts(y))) : missing values in object Does anyone know how to use the lag funciton and ccf together? 3) Suppose var1 and var2 are both of length 20. I would expect the correlation of the fourth lag of ccf(var1, var2) to be the same as lag zero of: ccf(var1[1:17], var2[4:20]), but they are not. Can someone explain why not? 4) How do I interpret the negative lags produced from the ccf function? [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html