Appending a list to a list of lists in R

Question

I m having issues appending data to a list which is already in a list format  I have a program which will export results objects during a simulation loop  The data itself is stored as a list of matrices  My idea is to store those lists in a list  and then save this list of lists as an R object for later analysis  however I m having some issues achieving this correctly  I ll show what I ve done with small abstract example just using values instead of the matrix data from my simulation   Say I ve run the simulation loop for 3 times  During the iterations  the results lists need to be collected into the one list of lists that I will save as an R object   List to contain the other lists and be saved   outlist1  lt - list    First iteration  resultsa  lt - list 1 2 3 4 5   outlist  lt - append outlist1 resultsa   Second Iteration  resultsb  lt - list 6 7 8 9 10   outlist  lt - append outlist1 b   Third Iteration  resultsc  lt - list 11 12 13 14 15   outlist  lt - list outlist2 c   However  this solution does not work with growing a list containing lists this way  the desired result is    gt outlist   1     1    1    1  1    1    2    1  2    1    3    1  3    1    4    1  4    1    5    1  5     2     2    1    1  6    2    2    1  7    2    3    1  8    2    4    1  9    2    5    1  10     3     3    1    1  11    3    2    1  12    3    3    1  13    3    4    1  14    3    5    1  15   However  instead what I get is    gt  outlist3   1     1    1     1    1    1    1  1    1    1    2    1  2    1    1    3    1  3    1    1    4    1  4    1    1    5    1  5     1    2     1    2    1    1  6    1    2    2    1  7    1    2    3    1  8    1    2    4    1  9    1    2    5    1  10   How do I grow a list  such that the resulting list formatted is like the desired result  If I do further analysis on these list I need to be able to easily access the elements

User · Answer

outlist  lt - list resultsa  outlist 2   lt - list resultsb  outlist 3   lt - list resultsc    append s help file says it is for vectors  But it can be used here  I thought I had tried that before but there were some strange anomalies in the OP s code that may have mislead me   outlist  lt - list resultsa  outlist  lt - append outlist list resultsb   outlist  lt - append outlist list resultsc     Same results

User · Answer

There are two other solutions which involve assigning to an index one past the end of the list  Here is a solution that does use append   resultsa  lt - list 1 2 3 4 5  resultsb  lt - list 6 7 8 9 10  resultsc  lt - list 11 12 13 14 15   outlist  lt - list resultsa  outlist  lt - append outlist  list resultsb   outlist  lt - append outlist  list resultsc     which gives your requested format   gt  str outlist  List of 3     List of 5         num 1         num 2         num 3         num 4         num 5     List of 5         num 6         num 7         num 8         num 9         num 10     List of 5         num 11         num 12         num 13         num 14         num 15

User · Answer

By putting an assignment of list on a variable first  myVar  lt - list     it opens the possibility of hiearchial assignments by  myVar  1    lt - list   myVar  2    lt - list     and so on    so now it s possible to do  myVar  1    1    lt - c      myVar  1    2    lt - c        or  myVar  1     subVar     lt - c        and so on  it is also possible to assign directly names  instead of     myVar   nameofsubvar    lt - list     and then  myVar   nameofsubvar     nameofsubsubvar     lt - c          important to remember is to always use double brackets to make the system work  then to get information is simple  myVar nameofsubvar nameofsubsubvar   and so on     example   a  lt -list   a   test     lt -list   a   test      subtest     lt - c 1 2 3  a  test  test subtest  1  1 2 3   a   test      sub2test     lt - c 3 4 5  a  test  test subtest  1  1 2 3   test sub2test  1  3 4 5   a nice feature of the R language in it s hiearchial definition     I used it for a complex implementation  with more than two levels  and it works

User · Answer

Could it be this  what you want to have     Initial list  myList  lt - list      Now the new experiments for i in 1 3     myList  length myList  1    lt - list sample 1 3      myList

User · Answer

The purrr package has a lot of handy functions for working on lists  The flatten command can clean up unwanted nesting  resultsa  lt - list 1 2 3 4 5  resultsb  lt - list 6 7 8 9 10  resultsc  lt - list 11 12 13 14 15   nested outlist  lt - list resultsa  resultsb  resultsc  outlist  lt - purrr  flatten nested outlist

User · Answer

Just a note on Brian s answer below  the first assignment to outlist can also be an append statement so you could also do something like this   resultsa  lt - list 1 2 3 4 5  resultsb  lt - list 6 7 8 9 10  resultsc  lt - list 11 12 13 14 15   outlist  lt - list   outlist  lt - append outlist list resultsa   outlist  lt - append outlist  list resultsb   outlist  lt - append outlist  list resultsc     This is sometimes helpful if you want to build a list from scratch in a loop

User · Answer

This answer is similar to the accepted one  but a bit less convoluted   L lt -list   for  i in 1 3    L lt -c L  list list sample 1 3

[r] Appending a list to a list of lists in R

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