
difft1d(1)                   Khoros                    difft1d(1)

PROGRAM
     difft1d - Inverse 1D Discrete Fourier Transform.

SYNTAX
     difft1d

     -i             input data file (xviff file)

     -o             resulting output file (xviff file)

     [-c]           select to center (0) or not to center (1) the
                    transform

     [-d]           data processing direction (0 = down vectors,
                    1 = across bands)

     [-s]           scale fft by 1, 1/N or 1/sqrt(N):
                    0 (Do not scale the output data),
                    1 (Scale output data by 1/N),
                    or 2 (Scale output data by 1/sqrt(N))
                       [default = 0]

     [-V]           Gives the version for difft1d

     [-U]           Gives the usage for difft1d

     [-P]           Prompts for command line options

     [-A [file1]]   Creates the answer file called difft1d.ans or
                    file1

     [-a [file1]]   Uses difft1d.ans or file1 as the answer file

DESCRIPTION
     performs the 1D inverse Fourier transform on a set of data
     sequences.  It can operate on Real and Complex data.  NOTE:
     complex data is expected to be in rectangular (not polar)
     form.  The output data type is VFF_TYP_COMPLEX.

     The transform can be centered about its N/2 term by setting
     the -c option to 1. (The default setting is not centered.)
     If -c is set to 0, the transform will not be centered.

     The output data can be scaled by 1/N or by 1/sqrt(N) if
     desired by using the -s option.  The default setting is to
     leave the output data unscaled (-s = 0).  If -s is set to 1,
     the output data is scaled by 1/N, where N in the number of
     points in the data sequence.  The output can be scaled by
     1/sqrt(N) by setting -s to 2.

     The default data processing direction for difft1d is in the
     vector direction.  This means that data stored in multiband
     format will be processed as a set of data sequences, where
     each sequence corresponds to a pixel location, and the
     points of each sequence are defined by the bands correspond-
     ing to that pixel location.  The direction of processing can
     be changed so that each band is processed as a signal
     (instead of each vector being a signal) by setting the -d
     option to 1.

REQUIRED ARGUMENTS
     -i     type: infile
            desc: input data file (xviff file)

     -o     type: outfile
            desc: resulting output file (xviff file)

OPTIONAL ARGUMENTS
     -c     type: boolean
            desc: select to center (0) or not to center (1) the
            transform
            default: false

     -d     type: boolean
            desc: data processing direction (0 = down vectors, 1
            = across bands)
            default: true

     -s     type: integer
            desc: scale fft by 1, 1/N or 1/sqrt(N)
            allowed values:
            0 (Do not scale the output data),
            1 (Scale output data by 1/N),
            or 2 (Scale output data by 1/sqrt(N))

EXAMPLES
     difft1d -i input_file -o output_file

     difft1d -i input_file -o output_file -s 1
     Computes the inverse FFT of input_file and scales the output
     by 1/N.

SEE ALSO
     intro(1), verror(3), vgparms(3), vutils(3), ldifft1d(3)

RESTRICTIONS
COPYRIGHT
     Copyright 1992, University of New Mexico.  All rights
     reserved.

Khoros                    Release: 1.0                          1

