Handling 2 and 3D data

If you have images or cubes that contain data that you want to view as spectra in some fashion, then SPLAT-VO will attempt to do this for you. There are three fundamental modes for doing this:

• by collapsing images into a single spectrum by adding together all values that lie perpendicular to the dispersion axis (so the spectrum runs along this axis, what a good spectral displaying tool should do),

• by expanding images and cubes into a spectrum for each line running along the dispersion axis,

• by vectorizing the whole data into a single line (created by joining everything line-by-line).

The default is to collapse. When collapsing cubes you have the option of which axis to step along selecting image planes, this is known as the select axis. To determine which option is used to handle your cubes or images you can either set values on the command-line, along with your spectra, or choose options in the open file dialogue. A command line that uses axis 3 as the dispersion axis and steps along axis 2 when choosing image planes might look like:

 % splat --ndaction collapse --dispax 3 --selectax 2 <spectral_cube> &

or in shorthand:

 % splat -n c -d 3 -s 2 <spectral_cube> &

If you don't choose a dispersion axis SPLAT-VO will make a good intelligent guess about this and step along the first axis that isn't the dispersion axis.