r - List of dataframes, how can I group every nth element? -

let's have list of dataframes called old_list:

#old_list list of length 10  #create vectors dfs (there's concise way this).   old_list<-list(rnorm(10),rnorm(10),rnorm(10),rnorm(10),rnorm(10),rnorm(10),                rnorm(10),rnorm(10),rnorm(10),rnorm(10))  #turn old_list df; add second column library('dplyr')  old_list<-lapply(old_list,function(x) as.data.frame(x)%>%mutate(mu=1)) 

ok, old_list looks this:

   [[1]]              x mu 1  -0.47734743  1 2   0.28986887  1 3   0.02933248  1 4  -2.15761840  1 5   0.32944305  1 6   0.33237442  1 7  -0.48621491  1 8  -0.61504793  1 9  -1.45353709  1 10 -1.22628027  1  [[2]]              x mu 1   0.10329026  1 2  -0.43502662  1 3   0.87865194  1 4  -0.37628634  1 5   0.06234334  1 6   0.35441583  1 7   0.46176186  1 8   1.98786158  1 9   1.81183387  1 10  2.18143130  1 .... 10th element 

i want go grouping every nth df in old_list new list called new_list. let's want group every second df. new_listshould have list of length 5 every element should contain 2 dfs. i've tried code this:

new_list<-list() (i in 1:seq(1,length(old_list),2)){   new_list[[i]]<-list(old_list[i:i+1])   } 

but doesn't 'group' 1st , 2nd, 3rd , 4th, 5th , 6th... dfs old_list i'd like. tips?

this first element of new_list should (i didn't set seed ignore different values of rnorm(10):

list(c(old_list[1],old_list[2])) [[1]] [[1]][[1]]              x mu 1   0.56877414  1 2  -2.35897500  1 3   1.16982547  1 4  -0.36609697  1 5   0.53758988  1 6  -1.05709000  1 7  -1.15997033  1 8  -0.07746139  1 9  -0.55179839  1 10 -0.11192844  1  [[1]][[2]]              x mu 1   0.34540644  1 2  -0.14567340  1 3  -0.56627562  1 4   0.22785077  1 5  -1.73692747  1 6  -1.03707293  1 7  -0.32093204  1 8   0.09449727  1 9   0.41419075  1 10 -0.17093046  1 

if need split list , nest elements based on 'n', use gl create grouping variable, split 'old_list' , convert tibble

library(tidyverse) n <- 2 map2(list(old_list), length(old_list),        ~split(.x, as.integer(gl(.y, n, .y)))) %>%        modify_depth(3, ~tibble(x = ., mu = 1)) 

---

or may this

n <- 2 res <- lapply(split(old_list, as.integer(gl(length(old_list), n,            length(old_list)))), function(x)            lapply(x, function(y) data.frame(x= y, mu = 1)))  res[1] #$`1` #$`1`[[1]] #             x mu #1   1.11696564  1 #2  -0.32362765  1 #3   0.07355866  1 #4   0.97178378  1 #5   0.55000016  1 #6   0.34958254  1 #7   1.32894403  1 #8  -1.02388909  1 #9   0.48285111  1 #10 -0.55077723  1  #$`1`[[2]] #            x mu #1  -0.4506403  1 #2   0.8701737  1 #3   3.3360928  1 #4   1.4608549  1 #5   1.1038983  1 #6   2.3979434  1 #7   0.1652383  1 #8   0.2294786  1 #9   0.2031739  1 #10 -0.4322401  1