setdiff two single column data frames

Question

I'm having a problem with a very simple issue and I don't know how to sort it out. Here's the deal. I have two one column data frames

a <- data.frame(C=c("c1","c2","c3","c4","c5","c6","c7","c8"))
b <- data.frame(C=c("c1","c4","c5","c8"))

I would like to get one column dataframe with the entries that do NOT appear in b but they are in a. ie. a dataframe with "c2","c3","c6","c7". I tried

c <- setdiff(a,b)

but I got the a dataframe and also with

c <- merge(a,b,all.x=TRUE)

I don't get what I want it. so do you know where I am wrong?

I must be honest. I dind't think about that... the only thing here is I don't get a data frame — Stefano, Nov 28 '15 at 18:38
you're right! :) and @akrun gave a compact solution herebelow. thanks a lot! — Stefano, Nov 28 '15 at 18:40

akrun · Accepted Answer · 2015-11-28T18:34:43.090

4

We can use anti_join

library(dplyr)
anti_join(a,b)

Or

data.frame(C= setdiff(a[,1], b[,1]))

edited Nov 28 '15 at 18:34

answered Nov 28 '15 at 18:33

akrun

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thanks! but is it really not possible with the base libraries? – Stefano Nov 28 '15 at 18:34
@Stefano You can use `setdiff` on the first columns – akrun Nov 28 '15 at 18:35

setdiff two single column data frames

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