3.17 The filter spectrum window

This window provides the ability to filter the current spectrum displayed in a plot.

The various options are:

• Average take the running average value over a number of positions.
• Rebin rebin a spectrum so that one output value equals the mean of a number of input values.
• Median take the running median value over a number of positions.
• Profile smooth the values using a profile matched to typical line shapes, Gaussian, Lorentzian and Voigt and the standard Hanning, Hamming, Welch and Barlett filters.
• Wavelet use various wavelet filters to convert the spectrum into multi-resolution coefficients, removing a fraction of the coefficients, thus denoising the spectrum.
• Spectrum smooth the values using a profile defined in another spectrum (allows you to create kernels that match some shape, rather than just the standard profiles).

You can define ranges of the spectrum to apply the filter over (except for Rebin, that always applies to the whole spectrum, which is what happens for all filters if you’ve not defined any ranges). Depending on whether you’ve selected Filter inside ranges or not the ranges are used to define the parts of the spectrum to filter, or not to filter. Parts which are not filtered do not form part of the result spectrum.

Command Buttons

• Filter Filters the spectrum and displays the result in the plot.
• Filter (Replace) Same as Filter, except the current spectrum is removed so you only see the filtered one.
• Reset Removes all filtered spectra (from the plot and global list) and erases the ranges.
• Reset (Replace) Also removes all filtered spectra, but restores the spectrum first removed by Filter (Replace) Effectively undoes the first Filter (Replace), since the last Reset (Replace)

Accelerator keys

• Control-f Apply current filter to spectrum.
• Control-l Apply current filter to spectrum and only display the new spectrum.
• Control-p Reset interface after a filter replace.
• Control-r Reset interface clearing any ranges and new spectra.
• Control-d Add a coordinate range (interactive or non-interactive).
• Control-e Delete the selected coordinate ranges.
• Control-w Close the window.
• F1 Display help on SPLAT-VO.
• Shift-F1 Display help on window.