小编Yur*_*enu的帖子

我有以下两个表:

df <- data.frame(eth = c("A","B","B","A","C"),ZIP1 = c(1,1,2,3,5))
Inc <- data.frame(ZIP2 = c(1,2,3,4,5,6,7),A = c(56,98,43,4,90,19,59), B = c(49,10,69,30,10,4,95),C = c(69,2,59,8,17,84,30))

eth    ZIP1         ZIP2    A    B    C
A      1            1      56   49   69
B      1            2      98   10   2
B      2            3      43   69   59
A      3            4      4    30   8
C      5            5      90   10   17
                    6      19   4    84
                    7      59   95   39

我想在df数据框中创建一个变量Inc,对于每个观察,该值是观察的eth和ZIP的交集.在我的例子中,它会导致:

   eth    ZIP1   Inc        
    A      1    56
    B      1    49
    B      2    10
    A      3    43 …