The UV_PREVIEW command
Keywords: imager

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### The `UV_PREVIEW` command

With large datasets, imaging can be long. [rgb]1,0,0IMAGER offers a simple, fast pre-imaging viewer through command magenta`UV_PREVIEW`.

This command will display the spectra obtained towards the phase center at several spatial scales (the default is for 4 tapers). It will also attempt to detect spectral features, by analyzing for each spectrum the noise statistics and the outliers. It performs automatic line identifications, using database(s) in the blue`LINEDB\` or ASTRO data format selected by command magenta`CATALOG`. Potential spectral lines in the band are displayed in blue, and detected ones in red. magenta`UV_PREVIEW` also warns the user about improper scaling of the data weights. The line emission region is indicated in grey.

The result of this automatic signal detection and line identification is saved in a SIC structure named blue`PREVIEW%`, that is automatically used by commands magenta`UV_BASELINE /CHANNELS` and magenta`UV_FILTER /CHANNELS` to respectively remove the continuum and filter the line emission to produce a continuum data set. The detected line frequencies are stored in blue`PREVIEW%FOUND%FREQ` and their names in blue`PREVIEW%FOUND%LINES`. This can be used to reference the velocity scale of the data to one of the detected lines, by using command magenta`SPECIFY FREQUENCY` `'PREVIEW%FOUND%FREQ[1]'` for example before further processing.

An example is shown in Fig

Figure: The magenta`UV_PREVIEW` output

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