column 1 : c(1,2,5,6)

column 2 : c(5,6,10,11)

i want to know how many (count) values from the two columns that is identical (so 5 and 6 is in both columns)

ps. in pandas it is "isin" but dont know about R

column 1 : c(1,2,5,6)

column 2 : c(5,6,10,11)

i want to know how many (count) values from the two columns that is identical (so 5 and 6 is in both columns)

ps. in pandas it is "isin" but dont know about R

This isn't too tricky to do, its just knowing which function to use!

```
one = c(1,2,5,6)
two = c(5,6,10,11)
common = intersect(one, two)
length(common)
```

`intersect()`

returns a vector containing common values in two vectors. The length of that is therefore the number of common items.

If these vectors are columns in a data frame, it looks very similar:

```
dat = data.frame(
one = c(1,2,5,6),
two = c(5,6,10,11)
)
common = intersect(dat$one, dat$two)
length(common)
```

Another alternative

```
one = c(1,2,5,6)
two = c(5,6,10,11)
sum(one %in% two)
#> [1] 2
```

^{Created on 2021-12-01 by the reprex package (v2.0.1)}

2 posts were split to a new topic: Help merging two data frames by a new column that doesn't share the same name

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