% @(#)correlline.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:55:39 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      plot_cali.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, spectroscopy
%.PURPOSE    On-line help file for the command: CORRELATE/LINE
%.VERSION    1.0  07-AUG-1992 : Creation, PB
%----------------------------------------------------------------
\se
SECTION./LINE
\es\co
CORRELATE/LINE                                        14-AUG-1992 PB
\oc\su
CORRELATE/LINE table_1 table_2 [pixel] [cntr,tol,rg,st] [pos,ref,wgt]
               [ref_value]  [outima]
	Cross-correlation between table columns.
\us\pu
Purpose:    Performs the cross-correlation between table columns.
            The elements on which the operation is performed can be
            selected by a reference column and a weighting column can
            be specified.
\up\sub
Subject:    Wavelength calibration, spectroscopy.
\bus\sy
Syntax:     CORRELATE/LINE table_1 table_2 [pixel] [cntr,tol,rg,st]
                           [pos,ref,wgt]  [refmin,refmax]  [outima]
\ys\pa
            table_1        = name of the first table
\ap\pa
            table_2        = name of the second table
\ap\pa
            pixel          = pixel step. This value is a scaling
                             factor for the following parameters tol,rg,st.
                             Default value is pixel = 1.
\ap\pa
            cntr,tol,rg,st = \\center,tolerance,range,step. \\
                             Defaults: 0., 0.05, 5., 0.1\\
                             The cross-correlation is performed in the range
                             (center - range*pixel) to (center + range*pixel). 
                             The shift is incremented by steps of step*pixel. 
                             The value tolerance*pixel is used to associate 
                             elements between the two tables (see Notes).
\ap\pa
            pos,ref,wgt    = Name of position, reference and weight columns.\\
                             Defaults: X,Y,+. It is assumed that the name of
                             these columns is the same for table_1 and table_2.
\\
                             The special symbol + can be used for the
                             reference and weight column to specify that
                             either no reference or no weight required.
\ap\pa
            refmin,refmax  = Minimum and maximum values in the reference
                             column. Default: +. The special symbol + can be 
                             used to specify that all the reference column 
                             must be considered.
\ap\pa
            outima         = Name of output cross-correlation image.
                             Default: middummx.bdf
\ap\no
Note:       
            a) The reference column is used as an additional condition
               to associate elements between the two tables. Two elements
               at positions (pos1) and (pos2) contribute to increment 
               the cross-correlation image at the value (shift) if:\\
               - the absolute value of the algebric sum (pos1-pos2+shift) is
                 smaller than tolerance*pixel.\\
               - the reference values are identical.\\
               The test on reference values is omitted if the special
               symbol plus (+) specifies the reference column.

            b) If values refmin and refmax are specified, the correlation 
               is performed only on the elements of the table which
               reference value is in the range [refmin,refmax]. Only
               one value refmin can be specified to indicate that the
               range is [refmin,refmin].

            c) Any selection set in table_1 or table_2 will be respected
               and the relevant elements ignored.

            d) The weight column can be used to modify the incrementation.
               A constant weight of value unity is used if the weight
               column is specified by the special symbol plus (+).
\on\exs
Examples:
\ex
            CORRELATE/LINE line  lined  0.25  ?   X,ORDER,PEAK  8,13 
\xe\sxe