Creation of data.table using a list #968

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1. arunsrinivasan commented on Dec 4, 2014

   

   arunsrinivasan

   on Dec 4, 2014

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   Thanks. Could you please read completely and follow the instructions here?

   Add the output you get wherever possible, comment the output, tell us which version you're using etc..
2. arunsrinivasan

   added

   Incomplete

   on Dec 4, 2014
3. richierocks commented on Dec 10, 2014

   

   richierocks

   on Dec 10, 2014

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   It's worth noting that as.data.table behaves as expected; it is only data.table that behaves differently.

   l <- list(x = 1:5, y = rnorm(5), z = letters[1:5])
   as.data.frame(l)
   ##   x           y z
   ## 1 1 -0.09738263 a
   ## 2 2  1.47511422 b
   ## 3 3  0.22953616 c
   ## 4 4  0.08974962 d
   ## 5 5  1.21911408 e
   data.frame(l)
   ##   x           y z
   ## 1 1 -0.09738263 a
   ## 2 2  1.47511422 b
   ## 3 3  0.22953616 c
   ## 4 4  0.08974962 d
   ## 5 5  1.21911408 e
   as.data.table(l)
   ##    x           y z
   ## 1: 1 -0.09738263 a
   ## 2: 2  1.47511422 b
   ## 3: 3  0.22953616 c
   ## 4: 4  0.08974962 d
   ## 5: 5  1.21911408 e
   data.table(l)
   ##                                                              l
   ## 1:                                                   1,2,3,4,5
   ## 2: -0.09738263, 1.47511422, 0.22953616, 0.08974962, 1.21911408
   ## 3:                                                   a,b,c,d,e
   

   Tested with today's devel version of data.table.
4. jangorecki commented on Dec 10, 2014

   

   jangorecki

   on Dec 10, 2014

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   data.table behave differently than data.frame but still behave as expected.
   What you do by data.table(l) is creating 1 column data.table which contains a list type column.
   How would you create below data.table if it wouldn't behave as it is now?

   structure(list(l = list(1:5, c(0.182844649428989, 0.858360447353789, 
   -0.0532774982161298, 0.459157422043729, 0.822852400527859), c("a", 
   "b", "c", "d", "e"))), .Names = "l", row.names = c(NA, -3L), class = c("data.table", 
   "data.frame"))
5. asantucci commented on Dec 10, 2014

   

   asantucci

   on Dec 10, 2014

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   as.data.table is what I was looking for.

   Thank you so much for all the follow up. I agree that the behavior is as
   expected for both data.table and as.data.table.

   Thank you for maintaining such an excellent package! It's really my
   favorite part of R.

   On Wed, Dec 10, 2014 at 1:46 PM, Jan Gorecki [email protected]
   wrote:

   data.table behave differently than data.frame but still behave as
   expected.
   What you do by datat.table(l) is creating 1 column data.table which
   contains a list column.
   How would would create below data.table if it wouldn't behave as it is now?

   structure(list(l = list(1:5, c(0.182844649428989, 0.858360447353789, -0.0532774982161298, 0.459157422043729, 0.822852400527859), c("a", "b", "c", "d", "e"))), .Names = "l", row.names = c(NA, -3L), class = c("data.table", "data.frame"))

   —
   Reply to this email directly or view it on GitHub
   #968 (comment)
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6. jangorecki commented on Dec 10, 2014

   

   jangorecki

   on Dec 10, 2014

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   @asantucci just don't forget to close this issue (assuming it is resolved) when you will have access to github (I see you did reply via email).
   PS. data.table is also my favorite part of R :)
7. asantucci

   closed this as completedon Dec 10, 2014
8. arunsrinivasan commented on Feb 8, 2015

   

   arunsrinivasan

   on Feb 8, 2015

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   I've noted this in #944 to expand on this point under FAQ. The underlying idea is to facilitate creation of list columns in a straightforward manner. If you've a list and would like to create a data.table then use as.data.table(); it's more appropriate.

   Also closing #877.