RESAMPLE

        ANALYSE\RESAMPLE Nx Xref Xval Xinc Unit [Shape] [Width] [/FFT]

    This  command  resamples a given spectrum on a specified X axis in given
    unit. The arguments are:
      Nx    the number of channels desired,
      Xref  the new reference channel,
      Xval  the value at the reference channel,
      Xinc  the new channel separation,
      Unit  either CHANNEL, VELOCITY or FREQUENCY to indicate the units used
            for Xval and Xinc.
      Shape  (optional)  a keyword for the frequency response of the synthe-
            sized channels:
            - TBOX means a rectangular function in the delay domain, as  for
              unsmoothed  correlator  channels (sin(pi.x)/(pi.x) in the fre-
              quency domain)
            - TPAR means a parabolic function in the delay  domain,  as  for
              smoothed  correlator  channels  (smoothing  function  used  at
              Plateau de Bure)
            - FBOX means a rectangular function in the frequency domain  (as
              for filterbank channels)
            - FTRIANGLE  means a triangular function in the frequency domain
              (as for filterbank channels, Hanning smoothed)
            By default the shape of the output channels is the same  as  the
            shape of the input channels.
      Width  (optional)  the  width  of  the output channels in units of the
            channel separation. The default (and minimum value) is 1.
    Using a wildcard '*' for any of these arguments  indicates  to  use  the
    same value as before.

    /FFT
        The  resampling is done in the delay domain and the data are Fourier
        transformed.  The Fourier transform is divided by the  transform  of
        the  input channel shape, then extrapolated by zeroes (if interpola-
        tion in the frequency domain is required), multiplied by the  trans-
        form  of  the desired channel shape, and finally transformed back to
        frequency domain. The output channel separation usually needs to  be
        slightly  rounded (to enable use of the FFT, the input spectrum must
        contain a round number of output channels).

    /NOFFT
        The output spectrum is a subset of the original one  if  their  axes
        are  aligned to a given precision. If not, the spectrum is resampled
        by direct interpolation. In this mode the exact  channel  separation
        requested  will  be  used. The counterpart to this technique is that
        correlation is introduced between adjacent channels and thus affects
        the  noise  intensity  (e.g. it is divided by sqrt(2) if the axis is
        shifted by half a channel). /NOFFT is the default behavior.

    The WIDTH parameter is used to provide an oversampled output spectrum if
    needed.

    The  shape of the input channels is derived from the backend number read
    in the telescope name for IRAM-30m  spectra:  TBOX  for  autocorrelator,
    FBOX for other (filter) backends. Otherwise, rectangular filter channels
    are assumed.