% @(#)sort_colu.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:11:30
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      sort_col.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, SORT/COL
%.PURPOSE    On-line help file for the command: SORT/COL
%.VERSION    1.0  19-JUN-1991 : Creation, PB
%----------------------------------------------------------------
\se
SECTION./COLUMN
\es\co
SORT/COLUMN						19-JUN-1991 PB
\oc\su
SORT/COLUMN input output
	column oriented sorting of the pixels of a frame.
\us\pu
Purpose:      
            Sort pixel values of a frame along columns
\up\sy
Syntax:       
            SORT/COL  input  output
\ys\pa
	    input  =   name of input frame
\ap\pa
            output =   name of output frame
\ap\no
Note:       This command enables to correct CCD images for bad columns
            patterns by the following procedure:

            If ima_org is the science frame containing bad columns,
            and ncol, nrow are respectively the number of columns and of 
            rows in ima_org. It is possible to prepare a mask of the 
            bad columns using:

                      SORT/COL    ima_org   ima_sort

                      AVERAGE/ROW mask1d =  ima_sort  @<row1>,@<row2>

                      where row1, row2 delimit an area of the sorted image
                      containing only pixels due to the background of
                      ima_org.

                      GROW/IMAGE  mask2d = mask1d  1.,1.,<nrow>

                      where nrow is the number of rows in ima_org.
                      Descriptors start and step of ima_org are
                      suppposed to be equal to 1.,1.

                      COMPUTE/IMA  ima_cor = ima_org - mask2d

                      This method is based on Pojmanski (1991, How To
                      Remove Easily the Unpleasant Column Pattern, 
                      Proceedings of the 3rd ESO/ST-ECF Data Analysis
                      Workshop, pp. 101-105)
\on\exs
Examples:
\ex
            none
\xe \sxe