How to transfer values from one dataframe to another? - r

Question

Consider the following code yielding the following dataframe
df1 <- data.frame("ID"=c("A", "A", "A", "A", "A", "B", "B", 'B', "B", "B"),
"X_A"=c(1,2,3,4,5,NA, NA, 8, 9,10), "X_B"=c(1,2,3,4,5,NA,NA, 8,9,10)
,"Y_A"=c(1,2,NA,NA, 10, 8,9,10,NA,NA), "Y_B"=c(1,2,NA, NA, 10,8,
9, 10, NA, NA))
it yields the following dataframe
ID X_A X_B Y_A Y_B
1 A 1 1 1 1
2 A 2 2 2 2
3 A 3 3 NA NA
4 A 4 4 NA NA
5 A 5 5 NA NA
6 B NA NA 8 8
7 B NA NA 9 9
8 B 8 8 10 10
9 B 9 9 NA NA
10 B 10 10 NA NA
I wish to transfer data from this dataframe to df2
ID X_A Y_A
1 A 1 1
2 A 2 2
3 A 3 3
4 A 4 4
5 A 5 5
6 A 6 6
7 A 7 7
8 A 8 8
9 A 9 9
10 A 10 10
11 B 1 1
12 B 2 2
13 B 3 3
14 B 4 4
15 B 5 5
16 B 6 6
17 B 7 7
18 B 8 8
19 B 9 9
20 B 10 10
The end data frame should be like this
ID X_A Y_A X_B Y_B
1 A 1 1 1 1
2 A 2 2 2 2
3 A 3 3 3 NA
4 A 4 4 4 NA
5 A 5 5 5 NA
6 A 6 6 NA NA
7 A 7 7 NA NA
8 A 8 8 NA NA
9 A 9 9 NA NA
10 A 10 10 NA NA
11 B 1 1 NA NA
12 B 2 2 NA NA
13 B 3 3 NA NA
14 B 4 4 NA NA
15 B 5 5 NA NA
16 B 6 6 NA NA
17 B 7 7 NA NA
18 B 8 8 8 8
19 B 9 9 9 9
20 B 10 10 10 10
The final output is like the result of a vlookup where, the ID and X_A, ID and Y_A columsn of df1 and df2 are matched so that the corresponding values of X_B and Y_B are filled in df2. In case there is no match, NA should result. I have tried the following code
merge(df1, df2).
this however slows down my system. I have also tried
library(dplyr)
df2 %>% right_join(df1, by=c(ID, x_A, y_A).
This results in all the rows appearing. Can the expected output be managed in R. request someone to help

Answer 1

Do you mean, join once on ID and X_A to get X_B, and afterwards ID and Y_A to get Y_B? Note that row 10 is different:
df2 %>%
left_join(select(df1, ID, X_A, X_B),
by = c("ID", "X_A")) %>%
left_join(select(df1, ID, Y_A, Y_B),
by = c("ID", "Y_A"))
# ID X_A Y_A X_B Y_B
# 1 A 1 1 1 1
# 2 A 2 2 2 2
# 3 A 3 3 3 NA
# 4 A 4 4 4 NA
# 5 A 5 5 5 NA
# 6 A 6 6 NA NA
# 7 A 7 7 NA NA
# 8 A 8 8 NA NA
# 9 A 9 9 NA NA
# 10 A 10 10 NA 10
# 11 B 1 1 NA NA
# 12 B 2 2 NA NA
# 13 B 3 3 NA NA
# 14 B 4 4 NA NA
# 15 B 5 5 NA NA
# 16 B 6 6 NA NA
# 17 B 7 7 NA NA
# 18 B 8 8 8 8
# 19 B 9 9 9 9
# 20 B 10 10 10 10
Base R:
want <- merge(df2, subset(df1, select = c(ID, X_A, X_B)), by = c("ID", "X_A"), all.x = TRUE)
(want <- merge(want, subset(df1, select = c(ID, Y_A, Y_B)), by = c("ID", "Y_A"), all.x = TRUE))