如何从不匹配的数据框中选择行? [英] How I can select rows from a dataframe that do not match?

问题描述

我正在尝试识别数据框中不匹配的值，但不知道如何执行此操作.

I'm trying to identify the values in a data frame that do not match, but can't figure out how to do this.

# make data frame 
a <- data.frame( x =  c(1,2,3,4)) 
b <- data.frame( y =  c(1,2,3,4,5,6))

# select only values from b that are not in 'a'
# attempt 1: 
results1 <- b$y[ !a$x ]

# attempt 2:  
results2 <- b[b$y != a$x,]

如果 a = c(1,2,3) 这有效，因为 a 是 b 的倍数.但是，我试图从数据框 y 中选择所有不在 x 中的值，并且不知道要使用什么函数.

If a = c(1,2,3) this works, as a is a multiple of b. However, I'm trying to just select all the values from data frame y, that are not in x, and don't understand what function to use.

推荐答案

如果我理解正确，您需要对 %in% 运算符取反.这样的事情应该可以工作:

If I understand correctly, you need the negation of the %in% operator. Something like this should work:

subset(b, !(y %in% a$x))

> subset(b, !(y %in% a$x))
  y
5 5
6 6

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