CODEWITHSUNDEEP
rlistloopsdataframelapply
rnorouzian
rnorouzian

Reputation: 7517

Extracting non-null elements from a list of list of data.frames in R

I have a list of list of data.frames called G.

In BASE R, I was wondering how I could separately extract elements dint and SD in A and B skipping any NULL elements?

My desired output is: dint = list(A = 1:3, B = c(1:4, 5:6) ) SD = list(A = 0:2, B = c(2:5, 3:4) )

Here is the data:

G <- list(A = list(short = NULL, short2 = NULL, del1 = data.frame(dint = 1:3, SD = 0:2), 
               del11 = NULL), 
          B = list(short = data.frame(dint = 1:4, SD = 2:5), short2 = NULL, del1 = 
               data.frame(dint = 5:6, SD = 3:4), del11 = NULL))

Upvotes: 1

Views: 129

Answers (2)

akrun
akrun

Reputation: 886948

We can just call a single lapply and extract the components

lapply(G, function(x) do.call(rbind, x)$dint)
#$A
#[1] 1 2 3

#$B
#[1] 1 2 3 4 5 6

Or to extract the 'SD'

lapply(G, function(x) do.call(rbind, x)$SD)  
#$A
#[1] 0 1 2

#$B
#[1] 2 3 4 5 3 4

It can be made into a function

f1 <- function(lstI, elementName){
            lapply(lstI, function(x) do.call(rbind, x)[[elementName]])
  }
f1(G, "dint")
f1(G, "SD")

rbind will get both the columns

lapply(G, function(x) do.call(rbind, x))

Upvotes: 1

Ronak Shah
Ronak Shah

Reputation: 388817

We could use nested lapply

lapply(G, function(x) unlist(lapply(x, `[[`, 'dint'), use.names = FALSE))

#$A
#[1] 1 2 3

#$B
#[1] 1 2 3 4 5 6

and similar for "SD" as well

lapply(G, function(x) unlist(lapply(x, `[[`, 'SD'), use.names = FALSE))

#$A
#[1] 0 1 2

#$B
#[1] 2 3 4 5 3 4

Upvotes: 1

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