;+
; NAME:
;  rt_szss96_kcoefv4
; PURPOSE: (one line)
;  return the k-coefficients for the CH4 nu4 band
; DESCRIPTION:
;  return the k-coefficients for the CH4 nu4 band
; CATEGORY:
;  RT
; CALLING SEQUENCE:
;  kcoef = rt_szss96_coefv4(t, icon)
; INPUTS:
;  t - temperature (K) [nz array]
;  icon - 1 for band A, 2 for band B
; OPTIONAL INPUT PARAMETERS:
; KEYWORD INPUT PARAMETERS:
;  codetype
;    'FORTRAN' - call routines from plutot.f
;    'FORTEST' - native IDL routines that reproduce the fortran
;    'IDL' - idl code, without the restriction of needing to reproduce fortran
; KEYWORD OUTPUT PARAMETERS:
;  none
; OUTPUTS:
;  kcoeff   number column density [nz,ng] (cm^2)
; COMMON BLOCKS:
; SIDE EFFECTS:
; RESTRICTIONS:
;  Modifies atm
; PROCEDURE:
; 
; EXAMPLE:
;
;  atm = rt_szss96_atmread('',0,code='FORTRAN')
; kcoef = rt_szss96_kcoefv4(atm.t, 2L)
; 
; MODIFICATION HISTORY:
;  Written 2007 Aug 31, Leslie Young SwRI
;  based on plutot.f, written by Zun Zhu
;-

function rt_szss96_kcoefv4, t, icon

    fcn = 'rt_szss96_kcoefv4'
    
    if not keyword_set(codetype) then codetype = 'FORTRAN'

    case codetype of
        'FORTRAN': begin
            get_ch4all,GG,WW,TREF
            if tref[0] ne 40.d then begin
                input6
            endif
            KM = n_elements(t)
            zkintemat,t,KM,XKZ,icon
            xkz_cgs = XKZ * 10.d
            ; mass of an AMU = k/R, using values of k, R from plutot.f
            kcoef = xkz_cgs * 16 * (1.3804D-16/8314d4)
            return, kcoef
        end
;        'FORTEST': begin
;            get_ch4all,GG,WW,TREF
;            if tref[0] ne 40.d then begin
;                input6
;                get_ch4all,GG,WW,TREF
;            endif
;            get_ch4v4,SIG4A,SIG4B
;           if icon eq 1 then lsig = alog(SIGA) else sig = alog(SIGB)
;           nz = n_elements(t)
;           ng = n_elements(gg)
;           for iz = 0, 
;           case (0) of
;               
;            endcase
;        end
        else: begin
            print, fcn, ': code type ', codetype, ' not implemented'
            return, -1
        end
    endcase

end