[Rd] Function to recognise convert dates between gregorian and other calendars (e.g. Persian)?

[Whit Armstrong]

probably easy to do w/ Boost DateTime

http://www.boost.org/doc/libs/1_37_0/doc/html/date_time.html

for which there is already an R package in development:
http://repo.or.cz/w/RBoostDateTime.git

I'm happy to write a small wrapper to do what you want if you can
offer a pseudocode example of the conversion function.

-Whit


On Wed, Jan 7, 2009 at 12:20 PM, Ted Byers <r.ted.byers at gmail.com> wrote:
> On Wed, Jan 7, 2009 at 10:23 AM, Amy Mikhail <amy.mikhail at googlemail.com>wrote:
>
>> Dear list,
>>
>> I will shortly have some data that contains numeric dates in the Persian /
>> Jalali calendar format, which I would like to convert to gregorian.  At the
>> moment there doesn't seem to be a function for this in R, but it would be
>> great if someone could come up with same - I would attempt it but the
>> algorithm is very complex and this is also way beyond my fairly rudimentary
>> knowledge of R.
>>
>> How do you feel about mixed language programming?
>
> I don't know anything about Jalali dates, but I took the time to check and
> found that Perl has modules that handle this (use CPAN or, on windows, PPM
> to find them).  However, like the C code you found, it will convert values a
> date at a time.  I don't know why this would be an issue.
>
> I have never tried to use either C or perl from within R, but if you can
> handle that, it would be trivial to apply these function calls to each value
> in a vector (or array if you prefer) in functions written in either C/C++ or
> perl.  In both C++ using STL and Perl, that would require only one line of
> code, and perhaps a couple more in C to manage the required loop if you
> restrict yourself to C, ignoring the benefits of C++.
>
> If I were doing this, I'd do it even before storing the data in my database,
> or at least before importing it into a dataframe in R, but that is primarily
> because I am still learning R, having used it for only a few months, rather
> than a few years using perl and 15+ years using C++.  I am so early on my R
> learning curve that I haven't yet looked at writing code in C++ or Perl that
> is to be called by R.  While I haven't read through it in enough detail to
> play seriously with it, the method for using such code from with R described
> in "Writing R Extensions<file:///C:/Program%20Files/R/R-2.8.0/doc/manual/R-exts.html>"
> seems simple enough.  Instead of writing the code to implement your
> 'complex' algorithm, why not just use the code you've found, or that
> available in CPAN (I don't know about you, but I hate reinventing the
> wheel), and create the trivial extension needed following the instructions
> in "Writing R Extensions<file:///C:/Program%20Files/R/R-2.8.0/doc/manual/R-exts.html>",
> or do it to the raw data before you import it into R?
>
> HTH
>
> Ted
>
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