如何在R的数据框中添加不同长度的列？

Question

I have two DFs as following:

df1

ID Borrower
 1   A 
 2   A 
 3   A

df2

ID Borrower Category
 1    A        X 
 1    A        X 
 1    A        X 
 2    A        X 
 2    A        X 
 2    A        X 
 3    A        X 
 3    A        X 
 3    A        X

I want to get the third column of df2 and add it to the first df. The final result that I want to get is something as following:

ID Borrower Category 
1     A       X 
2     A       X 
3     A       X

I tried df3<-left_join(df1, df2, by="ID", all=FALSE) but is not working. This code produces to me something similar like df2 (so ID=1,1,1,2,2,2,3,3,3). How can I add the column "Category" and get the desired result as presented above? Thank you:):)

Answer 1

This is because you have duplicate values in df2 . You could do:

library(tidyverse)
df1 <- tibble::tribble(
         ~ID, ~Borrower,
              1 ,  "A",
              2 ,  "A",
              3 ,  "A"
         )

df2 <- tibble::tribble(
         ~ID, ~Borrower, ~Category,
          1L,       "A",       "X",
          1L,       "A",       "X",
          1L,       "A",       "X",
          2L,       "A",       "X",
          2L,       "A",       "X",
          2L,       "A",       "X",
          3L,       "A",       "X",
          3L,       "A",       "X",
          3L,       "A",       "X"
         )

df1 %>% 
  left_join(distinct(df2)) 

Joining, by = c("ID", "Borrower")
# A tibble: 3 x 3
     ID Borrower Category
  <dbl> <chr>    <chr>   
1     1 A        X       
2     2 A        X       
3     3 A        X