Nested loop for sequential recoding - r

Question

I'm doing a sequence analysis on a large data sample. What I want to do is to rewrite my old Stata code in R, so that all of my analysis is performed in one single environment.
However, I would also like to improve it a little bit - the code is pretty long, and I would like to rewrite it using loops, so that it becomes more readable. Unfortunately my loop-writing skills are questionable.
1st loop [I think it needs to include an if statement]
I would like to write a loop for the following commands:
dt$dur.ofA1 <-(dt$M2_3R_A_1 - dt$M2_2R_A_1)
dt$dur.ofB1<-(dt$M2_3R_B_1 - dt$M2_2R_B_1)
dt$dur.ofC1<-(dt$M2_3R_C_1 - dt$M2_2R_C_1)
dt$dur.ofD1<-(dt$M2_3R_D_1 - dt$M2_2R_D_1)
dt$dur.ofE1<-(dt$M2_3R_E_1 - dt$M2_2R_E_1)
dt$dur.ofF1<-(dt$M2_3R_F_1 - dt$M2_2R_F_1)
dt$dur.ofG1<-(dt$M2_3R_G_1 - dt$M2_2R_G_1)
dt$dur.ofH1<-(dt$M2_3R_H_1 - dt$M2_2R_H_1)
dt$dur.ofA2<-(dt$M2_3R_A_2 - dt$M2_2R_A_2)
dt$dur.ofB2<-(dt$M2_3R_B_2 - dt$M2_2R_B_2)
dt$dur.ofC2<-(dt$M2_3R_C_2 - dt$M2_2R_C_2)
dt$dur.ofD2<-(dt$M2_3R_D_2 - dt$M2_2R_D_2)
dt$dur.ofE2<-(dt$M2_3R_E_2 - dt$M2_2R_E_2)
dt$dur.ofF2<-(dt$M2_3R_F_2 - dt$M2_2R_F_2)
dt$dur.ofG2<-(dt$M2_3R_G_2 - dt$M2_2R_G_2)
dt$dur.ofH2<-(dt$M2_3R_H_2 - dt$M2_2R_H_2)
dt$dur.ofA3<-(dt$M2_3R_A_3 - dt$M2_2R_A_3)
dt$dur.ofB3<-(dt$M2_3R_B_3 - dt$M2_2R_B_3)
dt$dur.ofC3<-(dt$M2_3R_C_3 - dt$M2_2R_C_3)
dt$dur.ofD3<-(dt$M2_3R_D_3 - dt$M2_2R_D_3)
dt$dur.ofE3<-(dt$M2_3R_E_3 - dt$M2_2R_E_3)
dt$dur.ofF3<-(dt$M2_3R_F_3 - dt$M2_2R_F_3)
dt$dur.ofG3<-(dt$M2_3R_G_3 - dt$M2_2R_G_3)
dt$dur.ofH3<-(dt$M2_3R_H_3 - dt$M2_2R_H_3)
My attempt:
db1 <- paste(rep("M2_", 24), "2R_", rep(LETTERS[seq( from = 1, to = 8)],3), "_",
rep(seq(from=1, to =3), 8),
sep = "")
db2 <- paste(rep("M2_", 24), "3R_", rep(LETTERS[seq( from = 1, to = 8)],3), "_",
rep(seq(from=1, to =3), 8),
sep = "")
dur <- paste(rep("dur.of", 24), rep(LETTERS[seq( from = 1, to = 8)],3),
rep(seq(from=1, to =3), 8),
sep = "")
dur <- as.list(dur)
for(e in dur){
for (j in db1){
for (i in db2){
{
dt[,e] <- dt[,i] - dt[,j]
}
I think the loop needs an if statement in the middle, so that it stops at a single item (subtracts A1 from A1, A2 from A2 etc.) from the list.
2) The second case is a little bit more complicated, but essentially it is the same case as described above:
The M2_2R_A_1 (start) M2_3R_A_1 (finish) indicate the yearly dates in which an educational activity took place. I would like to generate 1948:2013 variables that indicate that an activity took place in a particular year (stedu==x). A part of my Stata code is as follows (it goes on like that up to 2013):
recode stedu1948(0=2) if M2_2R_A_1<=1948 & 1948<= M2_3R_A_1 | M2_2R_A_2<=1948 & 1948<= M2_3R_A_2 | M2_2R_A_3<=1948 & 1948<= M2_3R_A_3
recode stedu1949(0=2) if M2_2R_A_1<=1949 & 1949<= M2_3R_A_1 | M2_2R_A_2<=1949 & 1949<= M2_3R_A_2 | M2_2R_A_3<=1949 & 1949<= M2_3R_A_3
recode stedu1950(0=2) if M2_2R_A_1<=1950 & 1950<= M2_3R_A_1 | M2_2R_A_2<=1950 & 1950<= M2_3R_A_2 | M2_2R_A_3<=1950 & 1950<= M2_3R_A_3
So in order to write a loop I would also need to include some conditions in order to stop the loop at a given point.

Answer 1

For your first item, use #thelatemail's suggestion. For second item, consider the following for loop using the ifelse() function:
for (i in 1948:2013) {
dt[[paste0("stedu", i)]] <- ifelse((dt$M2_2R_A_1 <= i & dt$M2_3R_A_1 >= i) OR
(dt$M2_2R_A_2 <= i & dt$M2_3R_A_2 >= i) OR
(dt$M2_2R_A_3 <= i & dt$M2_3R_A_3 >= i),
2,
dt[[paste0("stedu", i)]]
}