RESAMPLE

##
RESAMPLE

            ANALYSE\RESAMPLE Nx Xref Xval Xinc Unit [Shape] [Width] [/[NO]FFT]
            ANALYSE\RESAMPLE /LIKE GDFFile [/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. Changing the reference fre-
                quency or velocity has non trivial effects on the axis. Use  '='
                when possible (see below), else change the value with caution,
          Xinc  the new channel separation. In case of FREQUENCY resampling, the
                resolution is expected to be given in the restf frame.  However,
                RESAMPLE does not modify the current frame of the spectrum (i.e.
                the Doppler factor is left unchanged), so  the  input  frequency
                resolution will be corrected to the current frame.
          Unit  VELOCITY  or FREQUENCY for spectroscopic data, or ANGLE for con-
                tinuum drifts, to indicate the units used for Xval and Xinc.
          Shape (optional) a keyword for the frequency response of  the  synthe-
                sized  channels (see subtopic for details). 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 an equal sign '=' for any of these arguments indicates to use  the
        same  value as before. Using a wildcard '*' will choose an automatic de-
        fault:
          Nx    is set such as the last input and output channels are aligned,
          Xref  is set such as the first input and output channels are aligned,
          Xval  the reference frequency and velocity are left unchanged (same as
                =)
          Xinc  same as =
          Shape same as =
          Width same as =

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

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

Subsections

- RESAMPLE /FFT
- RESAMPLE /LIKE
- RESAMPLE SHAPE