[R] How to compare, match two columns from diferent dataframe and assign values from one datafram to the other

[Wang, Ying]

Dear R experts,

I'm new to R. It seems to be a simple question but I just can't find a way to do it. Please help me.

I have two data sets x and y as shown in the following. I want to compare the first two columns in x and y, find the matched ones and assign the relative value from column 2 of y to generate the third column of x. Any help wil be appreciated. Thanks.

> x
      [,1] [,2]
 [1,] "1"  "0"
 [2,] "2"  "0"
 [3,] "3"  "0"
 [4,] "4"  "0"
 [5,] "5"  "0"
 [6,] "6"  "0"
 [7,] "7"  "0"
 [8,] "8"  "0"
 [9,] "9"  "0"
[10,] "10" "0"
> y
     [,1] [,2]
[1,] "7"  "a"
[2,] "4"  "b"
[3,] "2"  "c"
[4,] "8"  "d"
[5,] "12" "e"
[6,] "15" "f"

The result I expect is:
x
      [,1] [,2] [,3]
 [1,] "1"  "0"  NA
 [2,] "2"  "0"  "c"
 [3,] "3"  "0"  NA
 [4,] "4"  "0"  "b"
 [5,] "5"  "0"  NA
 [6,] "6"  "0"  NA
 [7,] "7"  "0"  "a"
 [8,] "8"  "0"  "d"
 [9,] "9"  "0"  NA
[10,] "10" "0" NA


Best,

Ying