ungrouping dataframe in r which is grouped by rows - r

Question

I have this dataframe
Source: local data frame [159 x 2]
Groups: <by row>
# A tibble: 159 × 2
session_id requestId
* <int> <list>
1 1105 <int [3]>
2 1107 <int [2]>
3 1108 <int [6]>
4 1109 <int [1]>
5 1110 <int [6]>
6 1111 <int [8]>
7 1112 <int [4]>
8 1114 <int [8]>
9 1117 <int [7]>
10 1118 <int [4]>
# ... with 149 more rows
I dont know how to ungroup it or its not working as it is grouped by rows not by some variable ..
I want my output look like something in given pattern/format
# A tibble: 342 × 2
session_id requestId
<int> <dbl>
1 1105 10
2 1105 3
3 1107 13
4 1107 13
5 1108 4
6 1108 6
7 1109 12
8 1109 5
9 1110 6
10 1110 10
I dont know how to do it ,must be simple if known..Thanks for helping
Edit :-
structure(list(session_id = c(1105L, 1107L, 1108L, 1109L, 1110L,
1111L, 1112L, 1114L, 1117L, 1118L), requestId = list(c(8L, 14L,
20L), c(7L, 14L), c(1L, 7L, 8L, 20L, 16L, 17L), 8L, c(1L, 16L,
17L, 8L, 14L, 20L), c(1L, 7L, 8L, 20L, 4L, 11L, 13L, 14L), c(4L,
11L, 13L, 14L), c(6L, 8L, 14L, 2L, 4L, 10L, 15L, 18L), c(4L,
5L, 10L, 16L, 2L, 15L, 18L), c(20L, 1L, 7L, 8L))), .Names = c("session_id",
"requestId"), row.names = c(NA, -10L), class = c("tbl_df", "tbl",
"data.frame"))

Answer 1

Here's a possible starting point, although it's still missing a reproducible example. Can be edited when we get one:
tlengths <- sapply( tbl$requestId, length)
#Error in lapply(X = X, FUN = FUN, ...) : object 'tbl' not found
sessions <- mapply(rep, sessionId, tlengths)
#Error in mapply(rep, sessionId, tlengths) : object 'sessionId' not found
newtbl <- tibble(session_id=sessions, requestId=unlist(tbl$requestId))
#Error in tibble(session_id = sessions, requestId = unlist(tbl$requestId)) :
# could not find function "tibble"
library(tidyverse)

Answer 2

As -pkumar suggested in comment , I did this using tidyverse's unnest
df = structure(list(session_id = c(1105L, 1107L, 1108L, 1109L, 1110L,
1111L, 1112L, 1114L, 1117L, 1118L), requestId = list(c(8L, 14L,
20L), c(7L, 14L), c(1L, 7L, 8L, 20L, 16L, 17L), 8L, c(1L, 16L,
17L, 8L, 14L, 20L), c(1L, 7L, 8L, 20L, 4L, 11L, 13L, 14L), c(4L,
11L, 13L, 14L), c(6L, 8L, 14L, 2L, 4L, 10L, 15L, 18L), c(4L,
5L, 10L, 16L, 2L, 15L, 18L), c(20L, 1L, 7L, 8L))), .Names = c("session_id",
"requestId"), row.names = c(NA, -10L), class = c("tbl_df", "tbl",
"data.frame"))
library('tidyverse')
unnest(df)