% @(#)computcolu.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:43:20 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      computcolu.hlq
%.AUTHOR     KB, IPG/ESO
%.KEYWORDS   MIDAS, help files, COMPUTE/COLUMN
%.PURPOSE    On-line help file for the command: COMPUTE/COLUMN
%.VERSION    1.0  01-JUN-1987 : Creation, KB
%----------------------------------------------------------------
\se
SECTION./COLU
\es\co
COMPUTE/COLUMN					06-DEC-1994   KB
\oc\su
COMPUTE/COLUMN res_frame.column = arithmetic_expression
	do arithmetics on columns of an image
\us\pu
Purpose:
          Perform arithmetic operations on columns of images and store result
          in a column of an image.
\up\sy
Syntax:  
          COMPUTE/COLUMN res_frame.column = expression
\ys\pa
          res_frame.column = \\ image and column to get result of expression,
              the column is specified by Ci (or ci), with i in [1,NPIX(1)];
\\
              if VMS, a new version of the frame will be created by MIDAS
\ap\pa
          expression = expression with up to 10 operands, which may be
              functions and columns or/and constants in the usual algebraic
              notation, columns of the res_frame are indicated by a leading 
              "C" or "c";
\\
              columns of other frames are indicated via `frame.Ci'
\ap\no
Note: 
          The operations +, -, *, / and ** are supported with the same
          precedence as in FORTRAN. Parentheses may be used to change that
          order as well as to nest operations.
\\
          The functions SQRT(a), EXP(a), EXP10(a), LN(a), LOG10(a), SIN(a)
          ASIN(a), COS(a), ACOS(a), TAN(a), ATAN(a), INT(a), ATAN2(a1,a2),
          MAX(a1,a2), MIN(a1,a2), MOD(a1,a2) and ABS(a), are implemented as in
          FORTRAN. Except that INT(a) will return the nearest integer of "a"
          converted to real.
\\
          The trigonometric functions expect arguments in degrees!
\\
          Results of illegal operations (e.g. division by zero) are set to
          the "null value" defined by the keyword NULL.
\\
          This command does not work with 1-dim frames!
\\
          If columns from other frames are involved in the expression, they
          must have the same no. of pixels per column, i.e. NPIX(2).
          The no. of columns does not have to be the same.
\on\see
See also:
          COMPUTE/ROW, COMPUTE/PLANE, COMPUTE/IMAGE, COMPUTE/XYPLANE
\ees\exs
Examples:
\ex
          COMPUTE/COLUMN tiburon.C22 = C100+C44
            Use image frame `tiburon.bdf' and add the 100th column to the
            44th column, store the result into the 22nd column of frame
            `tiburon.bdf'.
\xe\ex
          COMPUTE/COLUMN ballena.c7 = 99.9*sin(delfin.c125)
            Set the 7th column of frame `ballena.bdf' to the product of 99.9
            and the sine of the contents of column no. 125 of frame 
            `delfin.bdf'. The no. of pixels per column of the two frames
            must be equal (i.e. same NPIX(2)).
\xe\ex
          COMPUTE/COLUMN ballena.c2 = 2.*c27
            Compute 2.0 * 27th column of `ballena.bdf' and store result into 
            second column of frame `ballena.bdf' .
\xe \sxe