Keywords: class

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## Continuum

So far, we have handled only Spectroscopic data, but Continuum data can be processed by CLASS . Currently, only continuum drifts can be reduced. The basic idea is to treat continuum drifts as spectra would be. Accordingly, very few commands behave differently in Continuum and Spectroscopy modes.

Continuum mode is accessed by typing the `SET TYPE` `CONTINUUM` command. The prompt then changes to `CAS>` (Continuum Analysis System). You can return to Spectroscopy mode later on typing the `SET TYPE SPECTROSCOPY or LINE` command and the prompt changes to `LAS>` (Line Analysis System).

Some commands have slightly different behaviour in Spectroscopy and Continuum modes.

- `SET UNIT` has no effect in Continuum mode.
- `SET ANGLE` also controls the plotting units in Continuum mode.
- `METHOD`: only `GAUSS` and `CONTINUUM` methods are allowed in Continuum mode.
- `LINES` has no effect with `CONTINUUM` method.
- `HEADER` uses a different format for Continuum and Spectroscopy modes.
- `STRIP` produces a map from a set of parallel drifts. The index must define such a set of drifts.
- FITS format support is experimental for continuum data.
- With `CONTINUUM` method, `PRINT FIT` command only outputs a single component, and the component number is not written.
- `SET ALIGN CHANNELS` and `SET ALIGN POSITION` are the only available alignment modes in Continuum mode.

Except for these restrictions, the behaviour of other commands is similar. Note that command `FIND` only selects data of the current type.

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