eddelbuettel commented on PR #692:
URL: https://github.com/apache/arrow-nanoarrow/pull/692#issuecomment-2542250701
This is nice. When running with numeric vectors it is even closer to
zero-copy as it looks like as we retain the buffer:
```r
> library(nanoarrow)
> df <- data.frame(x = 1:10)
> df$matrix_col <- matrix(1:20, ncol = 2, byrow = TRUE)
> array <- as_nanoarrow_array(df)
> array
<nanoarrow_array struct[10]>
$ length : int 10
$ null_count: int 0
$ offset : int 0
$ buffers :List of 1
..$ :<nanoarrow_buffer validity<bool>[null] ``
$ children :List of 2
..$ x :<nanoarrow_array int32[10]>
.. ..$ length : int 10
.. ..$ null_count: int 0
.. ..$ offset : int 0
.. ..$ buffers :List of 2
.. .. ..$ :<nanoarrow_buffer validity<bool>[null] ``
.. .. ..$ :<nanoarrow_buffer data<int32>[10][40 b]> `1 2 3 4 5 6 7 8 9 10`
.. ..$ dictionary: NULL
.. ..$ children : list()
..$ matrix_col:<nanoarrow_array fixed_size_list(2)[10]>
.. ..$ length : int 10
.. ..$ null_count: int 0
.. ..$ offset : int 0
.. ..$ buffers :List of 1
.. .. ..$ :<nanoarrow_buffer validity<bool>[null] ``
.. ..$ children :List of 1
.. .. ..$ item:<nanoarrow_array int32[20]>
.. .. .. ..$ length : int 20
.. .. .. ..$ null_count: int 0
.. .. .. ..$ offset : int 0
.. .. .. ..$ buffers :List of 2
.. .. .. .. ..$ :<nanoarrow_buffer validity<bool>[null] ``
.. .. .. .. ..$ :<nanoarrow_buffer data<int32>[20][80 b]> `1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20`
.. .. .. ..$ dictionary: NULL
.. .. .. ..$ children : list()
.. ..$ dictionary: NULL
$ dictionary: NULL
>
> convert_array(array, tibble::tibble(x = integer(), matrix_col =
matrix(integer(), ncol = 2)))
# A tibble: 10 × 2
x matrix_col[,1] [,2]
<int> <int> <int>
1 1 1 2
2 2 3 4
3 3 5 6
4 4 7 8
5 5 9 10
6 6 11 12
7 7 13 14
8 8 15 16
9 9 17 18
10 10 19 20
>
```
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