I have this type of DF
DF
ID V1
1 A
2 V
3 C
4 B
5 L
6 L
I would like to get
ID V1 V2
1 A AA
2 V AV
3 C AC
4 B BB
5 L BL
6 L BL
I would like to concatenate A, B in V1 with other characters in V1.
I used something like this
DF%>%
mutate(V2 = ifelse ((V1 == "A" ), paste ("A", ID), ifelse ((V1 == "B")), paste ("B",V1), "")%>%
V2 = na_if (V2, ""))%>%
fill (V2)
Here is a way using base R
df <- transform(df,
V2 = ave(x = V1,
cumsum(V1 %in% c("A", "B")), #grouping variable
FUN = function(x) paste0(x[1], x)))
Gives
df
# ID V1 V2
#1 1 A AA
#2 2 V AV
#3 3 C AC
#4 4 B BB
#5 5 L BL
#6 6 L BL
You can use %in% to find where A and B is. Use unsplit to replicate them and paste0 to make the new string.
i <- DF$V1 %in% c("A", "B")
DF$V2 <- paste0(unsplit(DF$V1[i], cumsum(i)), DF$V1)
#DF$V2 <- paste0(rep(DF$V1[i], diff(c(which(i), length(i)))), DF$V1) #Alternative
DF
# ID V1 V2
#1 1 A AA
#2 2 V AV
#3 3 C AC
#4 4 B BB
#5 5 L BL
#6 6 L BL
Here is a dplyr solution.
library(dplyr)
DF %>%
mutate(flag = cumsum(V1 %in% c("A", "B"))) %>%
group_by(flag) %>%
mutate(V2 = paste0(first(V1), V1)) %>%
ungroup() %>%
select(-flag)
## A tibble: 6 x 3
# ID V1 V2
# <int> <chr> <chr>
#1 1 A AA
#2 2 V AV
#3 3 C AC
#4 4 B BB
#5 5 L BL
#6 6 L BL
