Minus operation of data frames

Question

I have 2 data frames df1 and df2.

df1 <- data.frame(c1=c(\"a\",\"b\",\"c\",\"d\"),c2=c(1,2,3,4) )
df2 <- data.frame(c1=c(\"         


        

Answer 1

I remember coming across this exact issue quite a few months back. Managed to sift through my Evernote one-liners.

Note: This is not my solution. Credit goes to whoever wrote it (whom I can't seem to find at the moment).

If you don't worry about rownames then you can do:

df1[!duplicated(rbind(df2, df1))[-seq_len(nrow(df2))], ]
#   c1 c2
# 1  a  1
# 2  b  2

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Edit: A data.table solution:

dt1 <- data.table(df1, key="c1")
dt2 <- data.table(df2)
dt1[!dt2]

or better one-liner (from v1.9.6+):

setDT(df1)[!df2, on="c1"]

This returns all rows in df1 where df2$c1 doesn't have a match with df1$c1.