匹配R中的值[重复]

Question

这个问题在这里已有答案：

• How to tell what is in one vector and not another? 5个答案

说，我有数据集

mydat=structure(list(x1 = structure(c(2L, 3L, 4L, 5L, 1L), .Label = c("", 
"a", "b", "c", "d"), class = "factor"), x2 = structure(1:5, .Label = c("a", 
"b", "c", "d", "e"), class = "factor")), .Names = c("x1", "x2"
), class = "data.frame", row.names = c(NA, -5L))

x1 has values a,b,c,d
x2 has values a,b,c,d,e

如何显示x2 var中的值，但x1中没有？在我们的例子中，这是e值

作为我想要的输出

    Value
1   e

如果这个问题重复，请告诉我，我会删除它。

Answer 1

我们可以尝试

setdiff(mydat$x2,mydat$x1)
[1] "e"