Question

I have a nested liste, resulted from a function. Where the top element names are reapeated in the element names further down.

$`1`
$`1`$`1`
[1] 0 0 0 0 0 0 0 1 0

$`1`$`2`
[1] 0 0 0 0 0 0 0 0 0

$`2`
$`2`$`1`
[1] 0 0 0 1 1 0 0 0 0

$`2`$`2`
[1] 0 1 0 0 0 1 0 0 0

Is there a way to use an apply function (or whatever) to extract those vectors where the element and subelement names match. E.g. $1$1 and $2$2. I have a huge list (4000 elements with 4000 subelements) so efficiency is thus a must.

Alternatively – I have figured out a way out of this mess by using ´melt()´, but it’s too consuming for the size of my set. But if anyone know how to replicate the effect – giving a dataframe with 3 columns one for elementname, one for subelement name and one for the vector – that will also work.

Regards and thanks 🙂

Answer 1

This is a way to get a list of the vectors you want:

lapply(names(dat), function(x) dat[[x]][[x]])

In a data frame:

do.call("rbind",
        lapply(names(dat),
               function(x) data.frame(element = x,
                                      subelement = x,
                                      values = dat[[x]][[x]])
        )
)