COMPUTE

        [SIC\]COMPUTE OutVar OPERATION InVar [Parameters]

    Perform operations or transformations on variables that are not directly
    supported  by  the  array  capabilities  of the SIC command interpretor.
    OutVar is the output variable, InVar the input variable. Outvar must  be
    defined beforehand.

    The following operations are  available  on  REAL  and  DOUBLE_PRECISION
    arrays, regardless of their nature:
      - MAX     MIN     MEAN     RMS     SUM     PROD
        for which InVar is an array of rank 1 to 4 (a 1-D to 4-D array), and
        OutVar  must be an array of lesser rank (i.e., one or more dimension
        less than InVar, down to a number), AND of identical shape as  InVar
        for the dimensions in common.
        Example (if A[4,12,2,8] and b[4,12]): "COMPUTE B MAX A"
        Sections, implicit  transpositions,  etc...  permitted  by  SIC  are
        supported.
      - HISTOGRAM
        Example:  "COMPUTE  outvar  HISTOGRAM  invar  [hmin]  [hmax]  [bval]
        [eval]"
        which puts in variable 'outvar' (dimension [n,2]) the  histogram  of
        values  of  n-D variable 'invar', eventually between the cuts 'hmin'
        and 'hmax', and with blanking values 'bval'  and  'eval'  (that  is,
        values of the invar array are not taken in account for the histogram
        if at 'eval' from 'bval'). These Parameters can be absent.  One  can
        use '*' to omit any of them.

        The number of bins is dictated by the first dimension of  the  array
        min  of  the  'invar'  array.   The  'outvar'  variable contains the
        histogram in its first column (outvar[1]) and the corresponding  bin
        value in the second column (outvar[2]).

    The following transformations are available:
      - FFT+  (Direct Fast Fourier Transform)
      - FFT- (Inverse Fast Fourier Transform)
        which accept REAL or COMPLEX parameters. OutVar is a 2-D array  with
        second  dimension  equals  2,  storing  respectively  the  Real  and
        Imaginary part  of  the  (complex)  output  Fourier  transform.   By
        default,  InVar  is like OutVar, but if parameter REAL  is specified
        InVar is a 1-D array.
      - FOURT+ (Direct Fast Fourier Transform)
      - FOURT- (Inverse Fast Fourier Transform)
        Which operates on input and output on COMPLEX  Arrays  of  dimension
        [2,NX,NY]
      - COMPLEX
        Populates the Real part of  outvar  (complex  variable)  with  invar
        (real).
      - REAL
        outvar = REAL part of invar. Outvar is Real, Invar is Complex .
      - IMAG
        outvar = IMAGE part of invar. Outvar is Real, Invar is Complex.
      - ABS
        outvar = AMPLITUDE (invar). Outvar is Real, Invar is Complex.
      - PHASE
        outvar = PHASE (invar). Outvar is Real, Invar is Complex.
      - CMPMUL as in COMPUTE varout CMPMUL varin1 varin2:
        varout = PRODUCT of Varin1 and Varin2. All complex arrays.
    Miscellaneous Operations:
      - DATE as in COMPUTE creation_date DATE filename
        Where 'filename' is a file name and returns  the  last  modification
        date  in the integer variable 'creation_date'. Used in procedures to
        check if file has been changed, etc...
      - GAG_DATE as in COMPUTE idate GAG_DATE "15-DEC-2035"
        stores the date "15-DEC-2035" as  a  modified  Julian  date  in  the
        integer  variable  'idate'.  This  modified  julian  date has little
        meaning outside the rather sparse community of souls gathered around
        the CLASS program, however...