search for: newdfyear

...3 13 e 1998 1 2 3 14 e 1999 6 0 0"),head=TRUE,stringsAsFactors=FALSE)) I'd like to create new dataframes for each unique year in which for each value of A, the values of D, E and F are summed over the last 3 years (e.g. 1998 = 1998, 1997, 1996): Question 1: How do I go from DF to newDFyear? Examples: newDF1995 B D E F a 0 4 1 b 3 7 0 e 1 2 3 newDF1998 B D E F a 1 1 3 b 8 4 6 c 2 4 6 e 1 2 3 Then, for each new DF I need to generate a square matrix after doing the following: newDF1998$G<-newDF1998$D + newDF1998$E + newDF1998$F newDF1998$D<-newDF199...