[R] translating IDL to R

[Tom Roche]

I would appreciate

* guidance regarding translation of IDL routines to R, generally
* assistance translating two IDL routines to R, specifically

Why I ask:

I'm slowly learning how to do atmospheric modeling. One language that
has been been popular in this space is IDL

http://en.wikipedia.org/wiki/IDL_(programming_language)

which unfortunately is proprietary (not to mention butt-ugly, IMHO :-)
There is an emerging FOSS implementation, GDL

http://en.wikipedia.org/wiki/GNU_Data_Language

but I can't presently install GDL on either my own workstation or the
cluster on which I do my "real work." And, unfortunately, I need to
generate some datasets for which instructions are provided only in
IDL (see listings following my .sig). 

However I have R in both work environments, and love it. So if there
are any experts in IDL-to-R porting out there, I'd appreciate your
assistance.

TIA, Tom Roche <Tom_Roche at pobox.com>---2 IDL routines follow to EOF---

from ftp://gfed3:dailyandhourly@zea.ess.uci.edu/GFEDv3.1/Readme.pdf

;++++++++++++++++++++ idl code to generate daily emissions +++++++++
nlon=720 ; number of grid points by longitude
nlat=360 ; number of grid points by latitude
gfedmly=fltarr(nlon,nlat) ; array containing monthly emissions
gfeddly=fltarr(nlon,nlat) ; array containing daily emissions

; You must read monthly emissions to generate daily fluxes.
; For example, if you want daily emissions for January 21st, 2004,
; you need read monthly data in January 2004 first:
file0_in='GFED3.1_200401_C.txt'
file0_in=strcompress(file0_in, /REMOVE_ALL)
gfedmly = read_ascii( file0_in )
gfedmly = gfedmly.field001

; reverse the direction of latitude with monthly emissions
; to combine with daily fire fractions.
for j=1, nlat/2 do begin
  tmp = gfedmly[*,j-1]
  gfedmly[*,j-1] = gfedmly[*,nlat-j]
  gfedmly[*,nlat-j] = tmp
endfor
undefine, tmp

; Then, you can read daily fire fractions from the netcdf file.
file1_in = string('fraction_emissions_20040121.nc')
file1_in=strcompress(file1_in, /REMOVE_ALL)
fid=NCDF_OPEN(file1_in)
varid=NCDF_VARID(fid,'Fraction_of_Emissions')
NCDF_VARGET, fid, varid, DATA
NCDF_CLOSE, fid
gfeddly=gfedmly*DATA
;++++++++++++++++++++ the end for daily emissions ++++++++++++++++++

;++++++++++++++++++++ idl code to generate 3-hourly emissions ++++++
nlon=720 ; number of grid points by longitude
nlat=360 ; number of grid points by latitude
nhor=8 ; numbers of 3-hourly intervals each day
gfeddly=fltarr(nlon,nlat)       ; array containing daily emissions
gfed3hly=fltarr(nlon,nlat,nhor) ; array containing 3-hourly emissions

file_in = string('fraction_emissions_200401.nc')
file_in=strcompress(file_in, /REMOVE_ALL)
fid=NCDF_OPEN(file_in)
varid=NCDF_VARID(fid,'Fraction_of_Emissions')
NCDF_VARGET, fid, varid, DATA
NCDF_CLOSE, fid

for nh=0,nhor-1 do begin
  gfed3hly[*,*,nh]=gfeddly*DATA[*,*,nh]
endfor
;++++++++++++++++++++ the end for 3-hourly emissions +++++++++++++++