在 R 的两个命名列表之间应用 function 的最佳方法是什么？

Question

I have an S3 object structured like this:

dataset <- NULL
dataset$x <- list(a=runif(10), b=runif(10), c=runif(10))
dataset$y <- list(a=runif(10), b=runif(10), c=runif(10))

The two lists $x and $y contain an equal number of elements with the same names.

I need to apply a function between both lists simultaneously, as follows:

for(i in c('a','b','c')){
  subset <- dataset$x[[i]] > 0.5
  dataset$x[[i]] <- subset(dataset$x[[i]], subset)
  dataset$y[[i]] <- subset(dataset$y[[i]], subset)
}

In the real case, the lists have a very large number of elements, so a loop is not the fastest approach. What is the best way to vectorize this loop?

Thank you!

Answer 1

Here is one method with lapply/Map . Extract the 'x' element from 'dataset', convert the double list elements to logical ('lst1'). Then loop over the 'dataset' with lapply , use Map inside to subset the inner list with the logical list created with 'x' element ('lst1')

lst1 <- lapply(dataset$x,`>`, 0.5)
out <- lapply(dataset, function(x) Map(subset, x, lst1))

The advantage is that we don't have to extract the multiple list elements as showed in the OP's post

-output

out
$x
$x$a
[1] 0.6849740 0.7275233 0.8227778 0.9315966

$x$b
[1] 0.6296180 0.5122322 0.6795041

$x$c
[1] 0.5528317 0.9408803 0.7244978 0.6040235 0.8212669 0.5369701


$y
$y$a
[1] 0.1836949 0.8954276 0.5996935 0.4948389

$y$b
[1] 0.2699243 0.5965194 0.3989432

$y$c
[1] 0.5072449 0.1735438 0.4563791 0.9464107 0.7269070 0.4369199