;+
; NAME: DIMSTAT
;	
; PURPOSE:
;       To calculate the mean of the mean of the dark images, and 
;       the mean of the variance in the dark images passed to the
;       procedure AVERAGE.   
;	
; CATEGORY:
;	
; CALLING SEQUENCE:
;	DIMSTAT,C_NUMBER,MARR,VARR
;
; INPUTS:
;       C_NUMBER: A one-byte integer, specifying the camera number
;                 for which the dark image statitics are to be
;                 retrieved.
;
; KEYWORD PARAMETERS:
;       None.
;
; OUTPUTS:
;       MARR: A FLOAT ARRAY, containing the mean of the mean
;             of the dark images, indexed by CCD temperature
;             ranging from -49 to -31 deg C. at unit intervals.
;
;       VARR: A FLOAT ARRAY containing the mean of the variance
;             in the dark images, indexed by CCD temperature
;             ranging from -49 to -31 deg C. at unit intervals.
;
; COMMON BLOCKS:
;       None.
;
; SIDE EFFECTS:
;       None.
;
; RESTRICTIONS:
;       This procedure expects that the six following files
;       produced by the procedure AVERAGE exist:
;                                c:\idl\data\dark\number.0dk
;                                c:\idl\data\dark\sum.0dk
;                                c:\idl\data\dark\sqsum.0dk
;                                c:\idl\data\dark\number.1dk
;                                c:\idl\data\dark\sum.1dk
;                                c:\idl\data\dark\sqsum.1dk
;
; PROCEDURE:
;       Depending on whether the C_NUMBER is set to 0 or 1, one of the two
;       sets of three files, c:\idl\data\dark\number.0dk, 
;       c:\idl\data\dark\sum.0dk  and c:\idl\data\dark\sqsum.0dk or 
;       c:\idl\data\dark\number.1dk, c:\idl\data\dark\sum.1dk, and 
;       c:\idl\data\dark\sqsum.1dk, are opended for reading. In the files
;       ...\sum.0(1)dk , ...\sqsum.0(1) dk and ...\number.0(1)dk , are
;       the sum of images, the sum of squares of images and the number
;       of images used to produce these results, at a given CCD temperature
;       ranging from -49 to -31 deg C, at unit intervals, respectively.
;       Using each sum image , sum of square images and number of 
;       images, for a given CCD temperature, the  mean of the mean image
;       and the mean of the variance of the images is produced and stored
;       in the two arrays marr and varr, respectively.
;
; MODIFICATION HISTORY:
;       Written May 1994, by T A Oliynyk	
;       
;       June 7, 1994: The WHILE statement was added, and the CASE statement was
;                     shortened.
;-

PRO dimstat,c_number,marr,varr 

WHILE ((c_number NE 0) OR (c_number NE 1)) DO BEGIN

 print, 'Camera number (c_number) must be either a 0 or a 1'
 print, FORMAT='($,"Enter new Camera number: ")' & READ,c_number

ENDWHILE

CASE c_number OF 

 0: BEGIN

 OPENR,aunit,'c:\idl\data\dark\number.0dk',/GET_LUN  
 OPENR,bunit,'c:\idl\data\dark\sum.0dk',/GET_LUN  
 OPENR,cunit,'c:\idl\data\dark\sqsum.0dk',/GET_LUN  
 
 END

 1: BEGIN

 OPENR,aunit,'c:\idl\data\dark\number.1dk',/GET_LUN
 OPENR,bunit,'c:\idl\data\dark\sum.1dk',/GET_LUN
 OPENR,cunit,'c:\idl\data\dark\sqsum.1dk',/GET_LUN

 END

 marr=FLTARR(19)
 varr=FLTARR(19)

 n=ASSOC(aunit,LONARR(1)) 
 sum=ASSOC(bunit,LONARR(256,256)) 
 sqsum=ASSOC(cunit,LONARR(256,256)) 

 
 FOR i=0,18 DO BEGIN 

  m=TOTAL(n(i))

  IF m GE 2 THEN BEGIN 
 
   marr(i)=mean(sum(i)/m)                       
   varr(i)=mean((m*sqsum(i)-sum(i)^2)/(m*(m-1))) 

  ENDIF 
 ENDFOR
 
 FREE_LUN,aunit 
 FREE_LUN,bunit  
 FREE_LUN,cunit 
 
ENDCASE 
 
END