PRO lambdafit
;NAME:lambdafit
;
;PURPOSE:calibrate the wavelength for the SED mode -- fit a line to the 
;column number and the wavelength
;
;CALLING SEQUENCE: lambdafit
;
;INPUTS:name of file with wavelength in microns and the col #
; "LambdaCal.txt"
;
;OPTIONAL KEYWORD:
;
;OUTPUTS:"LambdaCol.txt" - lambda(0) an dispersion for each col and average
;for array
;
;SIDE EFFECTS:
;
;RESTRICTIONS:??
;
;EXAMPLES:
;
;MODIFICATION HISTORY:started on 3/3/03
;
;------------------------------------

name='LambdaCal.txt'
Close,10
OPENR,10, name

;spawn,'wc '+infile,wc_out
spawn,'wc '+name,wc_out
nlines = (strsplit(strtrim(wc_out[0]),/extract))[0]


dump=strarr(nlines)
lambda=strarr(nlines)
maxcol=strarr(nlines)
pound=strarr(nlines)

READF,10,dump
pound=strmid(dump,0,1)
lambda=(strmid(dump,3,14))
maxcol=(strmid(dump,15,30))
k=0
print, pound

FOR i=0,nlines-1 do begin
  IF (pound(i) ne '#') THEN BEGIN
   k=k+1
  ENdif
ENDFOR

xs=fltarr(k)
ys=fltarr(k)
xys=fltarr(k)
xsquare=fltarr(k)
k=0

FOR i=0,nlines-1 do begin
  IF (pound(i) ne '#') THEN BEGIN
   ys(k)=FLOAT(lambda(i))
   xs(k)=FLOAT(maxcol(i))
   k=k+1
  ENDIF
ENDFOR


for h= 0,k-1 DO Begin
   xys(h)=xs(h)*ys(h)
   xsquare(h)=xs(h)*xs(h)
;  xys(h)=lambda(h)*maxcol(h)
;  xsquare(h)=lambda(h)*lambda(h)
endfor

delta=(k*TOTAL(xsquare)-(TOTAL(xs))^2)
;Slope
 m=(k*TOTAL(xys)-TOTAL(xs)*TOTAL(ys))/delta
;y intercept
 b=(TOTAL(xsquare)*TOTAL(ys) - TOTAL(xs)*TOTAL(xys))/delta

PRINT, 'Dispersion= ',m
PRINT, 'Lambda(0)= ',b
PLOT, xs, (m*xs+b),ytit='wavelength in microns', xtit='row #'

;stop
END