r - R: remove rows from one data frame that are in another

Question

I have two data frames df1 and df2. They have the same (two) columns. I want to remove the rows from df1 that are in df2.

Answer 1

你可以用几个包来做到这一点。但这里是如何使用基础 R 来做到这一点。

df1 <-matrix(1:6,ncol=2,byrow=TRUE)
df2 <-matrix(1:10,ncol=2,byrow=TRUE)
all <-rbind(df1,df2) #rbind the columns
#use !duplicated fromLast = FALSE and fromLast = TRUE to get unique rows.
all[!duplicated(all,fromLast = FALSE)&!duplicated(all,fromLast = TRUE),] 

     [,1] [,2]
[1,]    7    8
[2,]    9   10

Answer 2

尝试这个：

df2 <-matrix(1:6,ncol=2,byrow=TRUE)
df1 <-matrix(1:10,ncol=2,byrow=TRUE)

data.frame(v1=setdiff(df1[,1], df2[,1]), v2=setdiff(df1[,2], df2[,2]))
  v1 v2
1  7  8
2  9 10

请注意，df1and与 Lapointe 的相同，但反之亦然，因为您想从 df1 中删除 df2中df2的行，因此 setdiff 会从中删除. 看xy?setdiff

你会得到与 Lapointe 相同的结果

Answer 3

考虑到您有一个在两个数据帧之间匹配的变量（var_match），我得到了一个简单的：

df_1_minus_2 <- df_1[which(!df_1$var_match %in% df_2$var_match),]