Conditions including comparison of consequtive elements within columns - r

Question

Could you please help me with the following task. Here is a template of my dataset:
Category <- c(1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3)
PrevRule <- c(-1, -1, -1, -1, -1, -1, -1, -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2)
UserRule <- c(2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 2, 2, 2, 2, 2, 2, 0, 0, 0, 1, 1, 1, 1)
Correct <- c(0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1)
df <- data.frame(Category, PrevRule, UserRule, Correct)
I need to create an additional PP column according to the following rules:
i is row index. n is maximum rows for each Category.
For Category == 1:
If Correct[i:i+2] == 0 then PP[i+2:n] = UserRule[i+2]
Else PP = NA
For Category > 1:
Do PP = PrevRule until Correct[i:i+2] == 0
Then PP[i+2:n] = UserRule[i+2]
So, in the end the PP column should look like in the following table (column starting with NA)
Category PrevRule UserRule Correct PP
1 1 -1 2 0 NA
2 1 -1 2 0 NA
3 1 -1 2 0 2
4 1 -1 1 1 2
5 1 -1 1 1 2
6 1 -1 1 1 2
7 1 -1 1 1 2
8 1 -1 1 1 2
9 2 1 1 0 1
10 2 1 1 0 1
11 2 1 2 1 1
12 2 1 0 0 1
13 2 1 0 0 1
14 2 1 0 0 0
15 2 1 2 1 0
16 2 1 2 1 0
17 2 1 2 1 0
18 2 1 2 1 0
19 2 1 2 1 0
20 3 2 2 0 2
21 3 2 0 0 2
22 3 2 0 0 2
23 3 2 0 0 0
24 3 2 1 1 0
25 3 2 1 1 0
26 3 2 1 1 0
27 3 2 1 1 0
Any advice and suggestions would be greatly appreciated!
Thank you!

Answer 1

It was realy difficult to understand what you ment, but here is my solution. It is not perfect as it uses a while-Loop but it should work:
ret <- array(dim = nrow(df))
i <- 1
while(i < nrow(df) - 3){
if(Category[i] == 1 & all(Correct[i + 0:2] == 0)){
tmp <- max(which(Category==1)) #end of category 1
ret[(i + 2):tmp] <- UserRule[i+2]
#set index i to the index-value of the last element in category 1
i <- tmp
}else{
ret[i] <- NA #actual not necessary, because PP is NA per default.
}
print("From now on, I will only ask clear questions!")
if(Category[i] >= 2){
ret[i] <- PrevRule[i]
if(all(Correct[(i-2):i] == 0)){#3 consecutive 0 in Correct
tmp <- max(which(Category == Category[i])) #end of current category
ret[i:tmp] <- UserRule[i]
i <- tmp #set index i to the index-value of the last element in the current category
}
}
i <- i + 1
}
df$PP <- ret