Combine lists in a list

Question

I have a list like

$`1`
[1] 1959   13

$`2`
[1] 2280  178   13

$`3`
[1] 2612  178   13

$`4`
[1] 2902  178   13

And the structure is something like:

structure(list(`1` = c(1959, 13), `2` = c(2280, 178, 13), `3` = c(2612, 
178, 13), `4` = c(2902, 178, 13)......,.Names = c("1", "2", "3", "4"....)

How can I combine the lists within this list and produce a list like:

$`list`
[1] 1959   13
[2] 2280  178   13
[3] 2612  178   13
[4] 2902  178   13

Can you use dput with your original list to show its exact structure? — David Robinson, Jul 30 '12 at 18:19
Your desired output looks just like your input. Could you also use dput to show (a sample of) the desired output? — Josh O'Brien, Jul 30 '12 at 18:28
Probably not what you're after, but if your list is in an object called `list`, you can use `str(list)` to print it so that it looks more like your desired output. — GSee, Jul 30 '12 at 19:29

Tyler Rinker · Accepted Answer · 2012-07-30T18:53:27.933

4

This is the closest I can get to what you're asking for as a matrix:

LIST <- structure(list(`1` = c(1959, 13), `2` = c(2280, 178, 13), `3` = c(2612, 
178, 13), `4` = c(2902, 178, 13)))

cbind.fill <-
function(...) {
    nm <- list(...)
    nm<-lapply(nm, as.matrix)
    n <- max(sapply(nm, nrow))
    do.call(cbind, lapply(nm, function(x) rbind(x, 
        matrix(, n - nrow(x), ncol(x)))))
}

t(do.call('cbind.fill', LIST))
print(X$list, na.print="", quote=FALSE)

Or using plyr

LIST <- lapply(LIST, function(x) data.frame(t(x)))
library(plyr)
rbind.fill(LIST)

Maybe you just don't want names ?

If so...

names(LIST) <- NULL
LIST

I think I just don't get the output structure you're after.

edited Jul 30 '12 at 18:53

answered Jul 30 '12 at 18:31

Tyler Rinker

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Thanks for your answer....I think I am confused with the list structure in R myself... – Seen Jul 30 '12 at 18:39
Think of it as an ordered container that you can throw anything into (matrix, dataframes, arrays, even another list) – Tyler Rinker Jul 30 '12 at 18:42

score 0 · Answer 2 · edited May 23 '17 at 12:13

Try the following code. The problem is that I'm not too sure what you want as your output; you're calling it a list but it looks an awful lot like matrix. Assuming that you do want it as a matrix, the following should do the trick:

x <- list()
x$`1` <- c(1959, 13)
x$`2` <- c(2280, 178, 13)
x$`3` <- c(2612, 178, 13)
x$`4` <- c(2902, 178, 13)

# maximum number of elements in any vector
max <- max(sapply(x, function(y) length(y)))

# make all vectors the same length
x <- lapply(x, function (y){length(y) <- max; y})

# combine them in a matrix
result <- do.call(rbind, x)

result:

> result
  [,1] [,2] [,3]
1 1959   13   NA
2 2280  178   13
3 2612  178   13
4 2902  178   13

You can always save this matrix output as an element of a list. I got the idea to make the lengths equal from here.

You won't be able to get rid of the NA if you want your matrix to be numeric (you can always turn it into characters and make the NA be "", but it's probably not a good idea for further work with the matrix).

It may be that I'm confused and that you want a list after all, but as Josh mentioned in his comment, your data is correct to begin with in that case.

I think you are right...I am somehow confused by the list structure of R myself..I think I need to convert my data into a matrix... — Seen, Jul 30 '12 at 18:38
Both Edward and I have shown how to turn your data into a matrix. — Tyler Rinker, Jul 30 '12 at 18:44

Combine lists in a list

2 Answers2