How to check if a row is a subset of a data.frame?

Question

Let's say we have this data.frame df

uid | aid | Freq
-----------------
 2  |  4  |  3
 9  |  1  |  2

How do we check if this row r <- data.frame(uid=9, aid=1) is in df

For vectors >> we use %in% but it didn't work here.

You can check with `merge(df, r)` – Pierre L Nov 29 '16 at 18:19 — Pierre L, Nov 29 '16 at 18:19
One idea: `any(duplicated(rbind(unique(df[names(r)]), r)))` – Rich Scriven Nov 29 '16 at 18:21 — Rich Scriven, Nov 29 '16 at 18:21

Pierre L · Accepted Answer · 2016-11-29T18:29:27.373

4

You can check with merge. Just be sure that column names match:

df <- head(mtcars)
r <- data.frame(mpg=18.1, cyl=6)
mrg <- merge(df, r)
#    mpg cyl disp  hp drat   wt  qsec vs am gear carb
# 1 18.1   6  225 105 2.76 3.46 20.22  1  0    3    1

There are many ways you can turn this into a logical test.

nrow(mrg) > 0

edited Nov 29 '16 at 18:29

answered Nov 29 '16 at 18:20

Pierre L

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so putting it in a condition form would be `if_else((merge(df, r) %>% nrow()) > 0, T, F)` – mabdrabo Nov 29 '16 at 18:21
2

@mabdrabo - Or `nrow(merge(df, r)) > 0` – Rich Scriven Nov 29 '16 at 18:23
@RichScriven, yes of course. It's just because I was going to add upon it. thanks :) – mabdrabo Nov 29 '16 at 18:24
Thanks @RichScriven – Pierre L Nov 29 '16 at 18:29
1

I might suggest approaching the problem without using merge: just select by row value: `any(r$uid == 9 & aid == 1)`. – JWLM Nov 29 '16 at 22:44

How to check if a row is a subset of a data.frame?

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