[R] Document mapping of Arrow <-> R types

[asfimport]

Expanded scope to include documenting all types.

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Previous description:

uint8, int16, uint16 -> int32

uint32 -> numeric

int64, uint64 -> ?

Reporter: Romain Francois / @romainfrancois
Assignee: Neal Richardson / @nealrichardson

Related issues:

• [R] collect int64, uint32, uint64 as R integer type if not out of bounds (is related to)

PRs and other links:

• GitHub Pull Request #7441

_{Note: This issue was originally created as ARROW-3446. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Thoughts about this? cc [~hadley] @javierluraschi

[asfimport]

Javier Luraschi / @javierluraschi:
Seems reasonable to me, in fact, I think this is already implemented as follows:

uint8, int16, uint16 -> int32

uint32 -> numeric

int64, uint64 -> bit64

So we can wait on @romainfrancois to confirm but this one can probably be closed.

[asfimport]

Wes McKinney / @wesm:
Can we close the loop on this, possibly documenting the issue?

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 7441
#7441