[R-sig-Epi] Converting dates from the Persian calendar to Gregorian

[Thomas Lumley]

I looked at the C code from Project Pluto that Hosseini references, and wrote R wrappers for it.  The C and R code are at
  http://faculty.washington.edu/tlumley/calendars

I haven't turned it into a package (anyone who wants to is welcome), and it has only been tested to a limited extent and only on Mac OS.

Build the C code with
   R CMD SHLIB convdates.c date.cpp
then source("convdates.R")

This sets up an OtherDate class that can hold Persian, Islamic, Hebrew, and the other calendars that the C code supports, with methods to convert to and from Date.

It should be possible to translate the C algorithms into straight R with little loss of efficiency, but that looked like more than an hour's work.

       -thomas



On Wed, 7 Jan 2009, BXC (Bendix Carstensen) wrote:

> Hi Amy,
> you probaly already have visited:
> http://www.codeproject.com/KB/cs/JalaliCalendar.aspx
> where the Iranian guy Homam Hosseini provides a discussion of the conversion, and some C code to do it.
>
> I am a C ignorant, but surely someone in the R-community would be able to take this code (and in collaboration with Homam) provide a function that converts Iranian / Jalali dataes to and from the Gregorian Date class??
>
> Best regards
> Bendix
>
>> -----Original Message-----
>> From: r-sig-epi-bounces at stat.math.ethz.ch
>> [mailto:r-sig-epi-bounces at stat.math.ethz.ch] On Behalf Of Amy Mikhail
>> Sent: 7. januar 2009 12:40
>> To: r-sig-epi at stat.math.ethz.ch
>> Subject: [R-sig-Epi] Converting dates from the Persian
>> calendar to Gregorian
>>
>> Dear Epi list,
>>
>> This is not a strictly epidemiological question, but an issue
>> that anyone might face if presented with a dataset containing
>> dates in a non-gregorian format.
>>
>> I am currently developing a database (in MS Access) for a
>> public health study, the results of which I intend to analyse
>> in R.  I have a small problem, in that the date each patient
>> visits the clinic will be entered into the database in the
>> Persian  / Jalali calendar format - e.g. today's
>> date in the Persian calendar is 18.10.1387.   For the
>> analysis however I
>> need these dates to be converted to Gregorian, so that I can
>> have months on the x axis of plots, etc.
>>
>> Does anyone know of a function / some code already written
>> that could do this conversion in R?  It is much too complex
>> for me to figure out (since the Persian new year starts on
>> 21st March, and although there are also 12 months they have
>> different lengths to gregorian months).  I'm guessing it
>> would require loops and such but this is beyond my current
>> level of R knowledge.
>>
>> I have found some online tools that do the conversion of
>> individual dates, but there seems to be nothing out there
>> that would convert a whole dataset's worth of dates.
>>
>> Any suggestions much appreciated,
>> With best wishes,
>> Amy
>>
>>
>> --
>> Amy Mikhail
>> Program Manager, ACTc Afghanistan Malaria Project London
>> School of Hygiene & Tropical Medicine HPRO, Charahi-e-Shahid,
>> Shar-e-Naw, Kabul, Afghanistan
>>
>> Email (Afg): amy.mikhail at googlemail.com
>> Email (UK): Amy.Mikhail at lshtm.ac.uk
>> Tel (Afg): +93 (0)706 126627
>> Tel (UK): +44 (0)781 4176107
>>
>> 	[[alternative HTML version deleted]]
>>
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Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle