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show dimensions of list columns with DT #3671

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randomgambit opened this issue Jun 30, 2019 · 4 comments · Fixed by #4154
Closed

show dimensions of list columns with DT #3671

randomgambit opened this issue Jun 30, 2019 · 4 comments · Fixed by #4154
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@randomgambit
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@randomgambit randomgambit commented Jun 30, 2019

Hello everyone,

I am all IN for a better integration of DT in the tidyverse ecosystem. DT is really great and I think some features of the tidyverse could be very useful in a DT setting.

In particular, I am a huge fan of purrr and list columns. Consider this.

> tibble(group = c(1,1,1,2,2,2),
+            val = list(list(1,2,3),list(1,2,3),list(1,2,3),
+                       list(1,2,3),list(1,2,3),list(1,2,3))) 
# A tibble: 6 x 2
  group val       
  <dbl> <list>    
1     1 <list [3]>
2     1 <list [3]>
3     1 <list [3]>
4     2 <list [3]>
5     2 <list [3]>
6     2 <list [3]>

As you can see, I can clearly see the dimension (or length) of each element of the list-column.
As far as I know, this is not possible with DT

>  data.table(group = c(1,1,1,2,2,2),
+            val = list(list(1,2,3),list(1,2,3),list(1,2,3),
+                       list(1,2,3),list(1,2,3),list(1,2,3))) 
   group    val
1:     1 <list>
2:     1 <list>
3:     1 <list>
4:     2 <list>
5:     2 <list>
6:     2 <list>

This is a bit unfortunate. Here the idea is to use furrr (which leverages purrr) to easily run computations in parallel across the list columns.


> mydf[,  newval := future_map(val, ~length(.x))]
> mydf
   group    val newval
1:     1 <list>      3
2:     1 <list>      3
3:     1 <list>      3
4:     2 <list>      3
5:     2 <list>      3
6:     2 <list>      3

Being able to see the dimension of the embedded list (or DT) is very important when one creates list columns with whole data.frames and run regressions on them. What do you think? Could the printing of DT show an output similar to the printing of the tibble?

Thanks!

@randomgambit
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@randomgambit randomgambit commented Jun 30, 2019

Similarly, this shows the dimensions of the embedded DT. Why not the opposite as well?


seq(1:3) %>% map(., ~ data.table(group = .x,
                                 mycol = seq(1, .x))) %>%
  enframe()
# A tibble: 3 x 2
   name value           
  <int> <list>          
1     1 <df[,2] [1 x 2]>
2     2 <df[,2] [2 x 2]>
3     3 <df[,2] [3 x 2]>

@franknarf1
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@franknarf1 franknarf1 commented Jun 30, 2019

Related maybe, re user-chosen printing rules: #3414 , #1523 (comment) (and other items in that thread)

Side note: future_map(val, ~length(.x)) looks like a lot of overhead for lengths(val) from base R..?

@randomgambit
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@randomgambit randomgambit commented Jun 30, 2019

@franknarf1 yes, thats. the future_map call was an example. In real life, I would run much more complex operations in parallel :)

@MichaelChirico
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@MichaelChirico MichaelChirico commented Jul 2, 2019

#3414 will indeed be the start to this

@jangorecki jangorecki changed the title feature request: show dimensions of list columns with DT show dimensions of list columns with DT Jul 30, 2019
@mattdowle mattdowle added this to the 1.12.9 milestone Jan 3, 2020
@jangorecki jangorecki removed this from the 1.12.11 milestone May 26, 2020
@jangorecki jangorecki added this to the 1.12.9 milestone May 26, 2020
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5 participants