Data Subsetting: Lists within list in R

Question

I have a list containing 100 lists within it, each of which has 552 numerical values. How do I sequentially extract the 1st value (and so on up to 552) from each of the 100 lists?

Example: 5 lists within a list containing the numbers 1-10

list(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), c(1, 2, 3, 4, 5, 6, 7, 
8, 9, 10), c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), c(1, 2, 3, 4, 5, 
6, 7, 8, 9, 10), c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))

I want to extract each term sequentially i.e. 1,1,1,1,1 and then 2,2,2,2,2 and so on

Can you give a small example (say a 10th of your actual data) with an indication of the output you expect too. — A5C1D2H2I1M1N2O1R2T1, Jan 20 '14 at 14:48
you can iterate over a list by key, and then iterate the object of inner list. — shakthydoss, Jan 20 '14 at 14:49
Something like this question perhaps: http://stackoverflow.com/questions/16179197/transpose-a-list-of-lists — Matthew Lundberg, Jan 20 '14 at 15:01

Matthew Lundberg · Accepted Answer · 2014-01-20T15:59:53.273

0

This statement produces a list of vectors, taking the first element of each of your original vectors, the second element, etc., giving NA for the value of a short vector:

num <-  max(unlist(lapply(x, length)))  ## Length of the longest vector in x

lapply(seq(num), function(i) unlist(lapply(x, `[`, i)))

And here's a matrix approach:

matrix(unlist(x), ncol=length(x))

The rows of that matrix are your elements. This relies on each vector being the same length.

edited Jan 20 '14 at 15:59

answered Jan 20 '14 at 15:04

Matthew Lundberg

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Cheers Matthew - I was being supremely daft; converting to a matrix solved all my problems!!! – Kvothe Jan 20 '14 at 15:19

Data Subsetting: Lists within list in R

1 Answers1