This is my dataframe:
df <- data.frame(ID = c(1,2,3), A1 = c("a1","a3","a5"),
B1 = c("b1","b3","b5"), A2 = c("a2","a4","a6"), B2 = c("b2","b4","b6"))
And the result I want is this:
ID A B
1 1 a1 b1
2 1 a2 b2
3 2 a3 b3
4 2 a4 b4
5 3 a5 b5
6 3 a6 b6
I tried to approach to a solution, but I had no luck.
We can use melt from data.table which can take multiple measure patterns to convert from 'wide' to 'long' format.
library(data.table)
melt(setDT(df), measure = patterns("^A", "^B"),
value.name = c("A", "B"))[, variable := NULL][order(ID)]
# ID A B
#1: 1 a1 b1
#2: 1 a2 b2
#3: 2 a3 b3
#4: 2 a4 b4
#5: 3 a5 b5
#6: 3 a6 b6
