### R Lagged Variables with Time-Series Cross-Sectional Data

If you want to create a lagged variable in R for time-series cross-sectional data the usual time series packages (i.e. zoo and xts) don’t really do the job.

So use the plyr package.

Imagine we have a data frame (Data) with three variables: Country, Year and Variable. We want to lag Variable one year for each country. Let’s call the lagged variable VariableLag1. Use the ddply command like this:


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


That’s it. Just remember to have the variables in time order.

Thanks to this post on StackOverflow.