PRO ns_linear, data, lincoeff, cordata, DATAQUALITY=dataquality, LINQUALITY=linquality, HISTORY=history, CALNAME=calname
;
;+
; NAME:
;       ns_linear
; PURPOSE:
;       Perform linearization correction on IR data
; CALLING SEQUENCE:
;       ns_linear, data, lincoeff, cordata[, quality, HISTORY=history,
;       CALNAME=calname]
; INPUTS:
;       data -- data array to correct
;       lincoeff -- array of correction coefficients
;       quality -- optional array of data quality
; OPTIONAL KEYWORD PARAMETERS:
;       dataquality -- data quality array
;       linquality -- linearity correction quality array
;       history -- output string array of reduction history
;       calname -- disk file name of correction coefficients
; OUTPUTS:
;       cordata -- corrected data
; COMMON BLOCKS:
;       none
; NOTES:
;       If lincoeff is a 2-D array, only the 1st-order correction is
;       applied, i.e. DATA' = DATA(1+coeff*DATA).  If lincoeff is a
;       3-D array, it must contain coefficients for _all_ orders,
;       including 0.
; EXAMPLE:
;       
; PROCEDURES CALLED:
;       none 
; MODIFICATION HISTORY:
; 1998/06/11 NAL/UCB created
;-

msg = n_elements(msgwid) GE 1
szd = size(data)
szl = size(lincoeff)
same = (szd(0:2) EQ szm(0:2))

IF (same(1) AND same(2)) THEN BEGIN ;same size data and coeff array
    IF szl(0) EQ 2 THEN BEGIN  ; only 1st-order corrections in coeff array
        lz = where(lincoeff EQ 0.0, nlz)
        IF nlz EQ szl(1)*szl(2) THEN BEGIN
            message, 'No non-zero coefficients.  No correction done.', /con
            IF msg THEN widget_control, msgwid, $
             set_value='No non-zero coefficients.  No correction done.'
            cordata = data
            return
        ENDIF 
        dcor = double(data)+double(lincoeff)*double(data)
    ENDIF ELSE BEGIN ; multi-order corrections in coeff array
        order = szl(0)
        dcor = dblarr(szd(1), szd(2))
        linarr = double(lincoeff)
        FOR i=1, order DO $
            dcor = temporary(dcor)+linarr(*, *, i-1)*data^i
    ENDELSE 
    cordata = dcor

    IF keyword_set(dataquality) THEN BEGIN ; if quality array is defined
        IF keyword_set(linquality) THEN badlin = where(linquality GT 1, ibl) $
         ELSE badlin = where(lincoeff(*, *, 0) LT 0, ibl)
        IF ibl GT 0 THEN dataquality(badlin) = dataquality(badlin)+16
    ENDIF 

    IF NOT keyword_set(calname) THEN calname = ' ' $
     ELSE calname = 'with coefficient file ' + calname
    IF n_elements(history) GT 0 THEN $
     history = [history, 'Linearization correction applied' + calname] $
     ELSE history = 'Linearization correction applied' + calname

ENDIF ELSE BEGIN
    errmsg = 'Linearization coefficient array not same size as data array.  No correction done.'
    message, errmsg, /con
    IF msg THEN widget_control, msgwid, set_value=errmsg
    cordata = data
ENDELSE 

return
END