AmagicalFishy - 1 year ago 57

R Question

I would like to split this into three chunks whose size is as equal as possible, in such a way that earlier chunks have more entries than later chunks if equality is *not* possible.

Say I have something like:

`x <- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 , 15, 16, 17, 18, 19)`

I'd like:

`[1]`

1, 2, 3, 4, 5, 6, 7

[2]

8, 9, 10, 11, 12, 13

[3]

14, 15, 16, 17, 18, 19

I can achieve this by defining my own function, using the length of

`x`

`x`

`split`

Answer Source

Use `seq_along`

to generate a vector of indices and use module division to divide it into three chunks, sort the indices and split on the sorted indices give the expected result:

```
split(x, sort((seq_along(x) - 1)%%3)) # -1 here to convert it to zero based indices so that
# extra elements will always stack from earlier chunks
# $`0`
# [1] 1 2 3 4 5 6 7
# $`1`
# [1] 8 9 10 11 12 13
# $`2`
# [1] 14 15 16 17 18 19
```