Date coercion

[imanuelcostigan]

Address #355:

• New as_date generic
• Methods for POSIXt, numeric and character vectors (per as.Date S3 methods) with sensible defaults
• Generic and methods are documented.

NB:

• Check passes except for one note regarding the following warning message:

@details [periods.r#1]: mismatched braces or quotes 

[vspinu]

It should probably be "convert".

[vspinu]

As to the commiting style, could you please keep related changes in one commit whenever possible? No need to split out documentation, roxigenization and news addition steps. All of these are a single change - adding one feature.

Also could you please add a test case as per #355?

[vspinu]

Hi Imanuel. What is the status of this? Do you plan to address my other comments and add tests? I would like to release by the end of this week. I can merge what you have so far and amend those myself if you don't have time.

[imanuelcostigan]

@vspinu I'm unlikely to get time before end of the week. In terms of commit style - sure. Suggest that you consider adding a CONTRIBUTING file to repo with this and other expectations.

[vspinu]

Ok. I will then merge manually your changes these days then leave for another shelve for 5-6 days before the final release. Will add the CONTRIBUTING file. Thanks for the idea.

[imanuelcostigan]

@vspinu found myself with some time tonight. Have added test cases and default method as requested.

[vspinu]

There are merge conflicts. I am merging it right now. By "default" I meant to use useAsDefault argument to setGeneric, but I guess this doesn't make any difference.

BTW, why do you need a method for "character"? as.Date does good job there. No?

[imanuelcostigan]

as.Date fine in that respect, but why not give users the same function call for everything? Of course, there is a performance hit by wrapping as.Date in an S4 method call, but I think users will appreciate unified call semantics. If they want performance, they can always call as.Date directly.

[vspinu]

Performance is not an issue. We are defaulting to as.Date anyways. So character input will drop into as.Date.character which seem to be doing a bit more than format = "%Y-%m-%d".

[imanuelcostigan]

Btw see https://github.com/blog/2141-squash-your-commits for setting your repo up to squash commits rather than requiring contributors to do so