### R +1 Lag

In the last post I gave an example of how to use R to lag a variable in a time-series cross-sectional data set by one time unit. In other words, the value of the lagged variable at time $$t$$ the lag would be the value of the unlagged variable at $$t-1$$.

Using the same example variables (Country, Year, Variable) here is how you would lag the variable (VariableLag1) back a year. So, in time t the value of VariableLag would be the value of Variable in $$t+1$$).

Here is the code:


library(plyr)
Data <- ddply(Data, .(country), transform, VariableLag1 =
c(Variable[2:(length(Variable))], NA)