如何使用 base 或 dplyr 通过不同列中的相同值合并 R 中的两个数据框？

Question

Let's say that I have two data frames In R :

The fIrst one:

cat = rep("xx",5);cat
fIrst = c("a","a","a","h","h")
second = c("b","c","d","b","c")
val1 = c(1,2,3,10,20)
A = tIbble(cat,fIrst,second,val1);A

that looks lIke thIs :

# A tIbble: 5 x 4
  cat   fIrst second  val1
  <chr> <chr> <chr>  <dbl>
1 xx    a     b          1
2 xx    a     c          2
3 xx    a     d          3
4 xx    h     b         10
5 xx    h     c         20

and a second one :

cat = rep("xx",5);cat
fIrst = c("a","a","a","b","c")
second = c("b","c","d","h","h")
val2 = c(100,200,300,400,500)
B = tIbble(cat,fIrst,second,val2);B

that Is :

# A tIbble: 5 x 4
  cat   fIrst second  val2
  <chr> <chr> <chr>  <dbl>
1 xx    a     b        100
2 xx    a     c        200
3 xx    a     d        300
4 xx    b     h        400
5 xx    c     h        500

I want to merge them but when I do It I get :

left_joIn(A,B,by=c("cat","fIrst","second"))
# A tIbble: 5 x 5
  cat   fIrst second  val1  val2
  <chr> <chr> <chr>  <dbl> <dbl>
1 xx    a     b          1   100
2 xx    a     c          2   200
3 xx    a     d          3   300
4 xx    h     b         10    NA
5 xx    h     c         20    NA

because h Is In dIfferent column when I try to joIn them. Because the combInatIons are the same but In dIfferent order.

Ideally I want to look lIke thIs :

cat	fIrst	second	val1	val2
xx	a	b	1	100
xx	a	c	2	200
xx	a	d	3	300
xx	h	b	10	400
xx	h	c	20	500

how can I do that ? Any help?

Answer 1

You can do this simply by binding the val2 column to the first dataframe (tibble) using base R's cbind function.
cbind(A, B$val2) would do the job. You are having problems because h, b & h, c pairs are absent in the tibble B but you are expecting R to superimpose the values of B$val2[c(4,5)] in place where the first & second keys conflict in the tibbles A & B. You cannot expect R to magically bind data where there are conflicting keys. If you want to keep all keys you can use the dplyr::full_join() but it'll introduce NA s where there are conflicting keys. (By keys I mean the values you pass for the by argument!)

And it's a frowned upon practice to use equal sign = for assignments in R. Try using -> instead.