;+
;
; @file_comments
; interpolate data from an irregular 2D grid to any 2D grid.
;   Only 1 method available = bilinear
;
; @categories 
; Interpolation
;
; @param method {in}{required}{type=string}
; a string defining the interpolation method. must be 'bilinear'
;
; @param datain {in}{required}{type=2d array}
; a 2D array the input data to interpolate
;
; @param lonin {in}{optional}{type=2d array}
; a 2D array defining the longitude of the input data
;
; @param latin {in}{optional}{type=2d array}
; a 2D array defining the latitude of the input data.
;
; @param mskin {in}{optional}{type=2d array}
; a 2D array, the land-sea mask of the input data (1 on ocean, 0 on land)
;
; @param lonout {in}{optional}{type=1d or 2d array}
; 1D or 2D array defining the longitude of the output data.
;
; @param latout {in}{optional}{type=1d or 2d array}
; 1D or 2D array defining the latitude of the output data.
;
; @param mskout {in}{required}{type=2d array}
; a 2D array, the land-sea mask of the output data (1 on ocean, 0 on land)
;
; @keyword WEIG {type=2d array}
; (see ADDR)
;
; @keyword ADDR {type=2d array}
; 2D arrays, weig and addr are the weight and addresses used to
; perform the interpolation:
;          dataout = total(weig*datain[addr], 1)
;          dataout = reform(dataout, jpio, jpjo, /over)
; Those keywords can be set to named variables (that are undefined or equal to 0) into which the
; values will be copied when the current routine exits. Next, they can be used to perform
; the interpolation without computing again those 2 parameters. This greatly
; speed-up the interpolation! In that case, lonin, latin, lonout and latout are not necessary.
;
; @returns
; 2D array the interpolated data
;
; @restrictions
; We supposed the data are located on a sphere, with a periodicity along
; the longitude.
; Note that the input data can contain the same cells several times
; (like ORCA grid near the north pole boundary)
;
; @examples
;
; IDL> tncep = fromirr('bilinear', topa, glamt, gphit, tmask[*,*,0], lonout, latout, mskout)
;
;  or
;
; IDL> t1ncep = fromirr('bilinear', topa, glamt, gphit, tmask[*,*,0], lonout, latout, mskout $
;                            , WEIG = a, ADDR = b)
; IDL> help, a, b
; IDL> t2ncep = fromirr('bilinear', topa, WEIG = a, ADDR = b)
;
; @history
;  June 2006: Sebastien Masson (smasson\@lodyc.jussieu.fr)
;
; @version $Id$
;
;-
;----------------------------------------------------------
;----------------------------------------------------------
;
FUNCTION fromirr, method, datain, lonin, latin, mskin, lonout, latout, mskout $
                  , WEIG = weig, ADDR = addr
;
  compile_opt strictarr, strictarrsubs
;
;---------------
; atmospheric grid parameters
;---------------
    alon = lonin
    alat = latin
    get_gridparams, alon, alat, jpia, jpja, 2, /double
;---------------
; Oceanic grid parameters
;---------------
    olon = lonout
    olat = latout
    get_gridparams, olon, olat, jpio, jpjo, 2, /double
;---------------
; Compute weight and address
;---------------
  IF NOT (keyword_set(weig) AND keyword_set(addr)) THEN BEGIN
    CASE method OF
      'bilinear':compute_fromirr_bilinear_weigaddr, alon, alat, mskin, olon, olat, mskout, weig, addr
      ELSE:BEGIN
        print, ' unknown interpolation method... we stop'
        stop
      ENDELSE
    ENDCASE
  ENDIF
;---------------
; to the interpolation
;---------------
  dataout = total(weig*datain[addr], 1)
  dataout = reform(dataout, jpio, jpjo, /over)
;
  RETURN, dataout
END