Question

I have been looking at mapply documentation but I cannot find an example close enough to help me get started.

I have lists foo and bar:

set.seed(123)
f   <- data.frame(y=1:10,x=sample(LETTERS,10))
foo <- list(f,f)
b   <- data.frame(x=c("J","U","A"))
ba  <- data.frame(x=c("J","W"))
bar <- list(b,ba)

I can subset f with b using:

result <- f[f$x %in% b$x ,]

I want to do this subset but for the whole lists foo and bar i.e. subset foo[[1]] by foo[[1]]["x"] on bar[[1]] and foo[[2]] by foo[[2]]["x"] on bar[[2]] etc…

the result would be:

>foo
[[1]]
    y x
3   3 J
4   4 U
6   6 A

[[2]]
    y x
3   3 J
5   5 W

Answer 1

Like so…?

mapply(merge,foo,bar,SIMPLIFY = FALSE)
[[1]]
  x y
1 A 6
2 J 3
3 U 4

[[2]]
  x y
1 J 3
2 W 5