R - Collapse into vector same member of a list - r

Question

I have a list with same structure for every member as the following
config <- NULL
config[["secA"]] <- NULL
config[["secA"]]$VAL <- 0
config[["secA"]]$ARR <- c(1,2,3,4,5)
config[["secA"]]$DF <- data.frame(matrix(c(1,5,3,8),2,2))
config[["secB"]] <- NULL
config[["secB"]]$VAL <- 1
config[["secB"]]$ARR <- c(1,3,2,4,9)
config[["secB"]]$DF <- data.frame(matrix(c(2,6,1,9),2,2))
config[["secC"]] <- NULL
config[["secC"]]$VAL <- 5
config[["secC"]]$ARR <- c(4,2,1,5,8)
config[["secC"]]$DF <- data.frame(matrix(c(4,2,1,7),2,2))
and I need to obtain 3 vectors VAL, ARR and DF, each with the concatenated elements of the corresponding member. such as
# VAL: 0,1,5
# ARR: 1,2,3,4,5,1,3,2,4,9,4,2,1,5,8
# DF: 1,5,3,8,2,6,1,9,4,2,1,7
Looking at similar situations, I have the feeling I need to use a combination of do.call and cbind or lapply but I have no clue. any suggestions?

Answer 1

config <- NULL
config[["secA"]] <- NULL
config[["secA"]]$VAL <- 0
config[["secA"]]$ARR <- c(1,2,3,4,5)
config[["secA"]]$DF <- data.frame(matrix(c(1,5,3,8),2,2))
config[["secB"]] <- NULL
config[["secB"]]$VAL <- 1
config[["secB"]]$ARR <- c(1,3,2,4,9)
config[["secB"]]$DF <- data.frame(matrix(c(2,6,1,9),2,2))
config[["secC"]] <- NULL
config[["secC"]]$VAL <- 5
config[["secC"]]$ARR <- c(4,2,1,5,8)
config[["secC"]]$DF <- data.frame(matrix(c(4,2,1,7),2,2))
sapply(names(config[[1]]), function(x)
unname(unlist(sapply(config, `[`, x))), USE.NAMES = TRUE)
# $VAL
# [1] 0 1 5
#
# $ARR
# [1] 1 2 3 4 5 1 3 2 4 9 4 2 1 5 8
#
# $DF
# [1] 1 5 3 8 2 6 1 9 4 2 1 7
Or you can use this clist function
Unfortunately there were no other answers.
(l <- Reduce(clist, config))
# $VAL
# [1] 0 1 5
#
# $ARR
# [1] 1 2 3 4 5 1 3 2 4 9 4 2 1 5 8
#
# $DF
# X1 X2 X1 X2 X1 X2
# 1 1 3 2 1 4 1
# 2 5 8 6 9 2 7
It merges data frames and matrices, so you need to unlist to get the vector you want
l$DF <- unname(unlist(l$DF))
l
# $VAL
# [1] 0 1 5
#
# $ARR
# [1] 1 2 3 4 5 1 3 2 4 9 4 2 1 5 8
#
# $DF
# [1] 1 5 3 8 2 6 1 9 4 2 1 7
Function
clist <- function (x, y) {
islist <- function(x) inherits(x, 'list')
'%||%' <- function(a, b) if (!is.null(a)) a else b
get_fun <- function(x, y)
switch(class(x %||% y),
matrix = cbind,
data.frame = function(x, y)
do.call('cbind.data.frame', Filter(Negate(is.null), list(x, y))),
factor = function(...) unlist(list(...)), c)
stopifnot(islist(x), islist(y))
nn <- names(rapply(c(x, y), names, how = 'list'))
if (is.null(nn) || any(!nzchar(nn)))
stop('All non-NULL list elements should have unique names', domain = NA)
nn <- unique(c(names(x), names(y)))
z <- setNames(vector('list', length(nn)), nn)
for (ii in nn)
z[[ii]] <- if (islist(x[[ii]]) && islist(y[[ii]]))
Recall(x[[ii]], y[[ii]]) else
(get_fun(x[[ii]], y[[ii]]))(x[[ii]], y[[ii]])
z
}

Answer 2

Another approach, with slightly less code.
un_config <- unlist(config)
un_configNAM <- names(un_config)
vecNAM <- c("VAL", "ARR", "DF")
for(n in vecNAM){
assign(n, un_config[grepl(n, un_configNAM)])
}
This will return 3 vectors as the OP requested. However, generally it is more advantageous to store results in a list as rawr suggests. You of course can adopt the above code so that results are stored within a list.
l <- rep(list(NA), length(vecNAM))
i = 1
for(n in vecNAM){
l[[i]] <- un_config[grepl(n, un_configNAM)]
i = i +1
}