\section{Advanced Data Analysis}
\label{sec:analysis}

Besides basic interferometric imaging, \imager{} offers a number
of advanced tools that can be used to extract more information from
the available data than just by visual inspection of the deconvolved
images.

These tools are particularly useful for weak signal detection.
Some of them are generic (e.g. the Matched Filtering), others 
specific of some astrophysical situations (e.g. the \texttt{KEPLER} tool)

\subsection{Matched Filtering}

Weak signal detection is always an issue in most astrophysical cases
(e.g. high redshift galaxies, faint lines in proto-planetary disks,
to cite some).

For spectral lines, \imager{} offers the \com{UV\_DETECT} command,
that uses an image model as an optimal filter to enhance weak line
detection.  This is a generic tool, that can use an observed data
cube (from a strong line, presumably) as the image model, or the
result of a simulation.

\subsection{Line Stacking}

Another aspect is spectral line stacking, when several lines are
assumed to follow the same spatial distribution. This can be
done using command \comm{UV\_MERGE}{/MODE STACK}. The stacked UV table result
can be imaged and analyzed as usual. Like \qom{UV\_DETECT},
\qom{UV\_MERGE} does not make any assumption on the source shape.

\subsection{Rotationally symmetric (thin) structures: Keplerian disks}

The \com{KEPLER} command re-aligns in velocity the spectra as a function
of radius (distance from the rotation center), by correcting from
the projection effect and radial velocity law. This allows to
stack spectra coming from the same radius, and thus to derive
radial profiles.

The result is a Position-Velocity image, and can be displayed conveniently
with the \comm{SHOW}{KEPLER} command.

The \qom{KEPLER} command assumes by default that the velocity law is Keplerian. 
However, arbitrary analytic laws can be used (see \comm{KEPLER}{/VELOCITY}, so that
the tool can also be used for example for spectral lines in galaxies.

\subsection{Image Handling and Comparison}

The  \qom{MAP\_*} suite of commands (\qom{MAP\_COMBINE}, \qom{MAP\_COMPRESS}, \qom{MAP\_INTEGRATE}
\qom{MAP\_REPROJECT}, \qom{MAP\_RESAMPLE}, \qom{MAP\_SMOOTH} and \qom{MAP\_CONTINUUM})
allow basic operations on Data Cubes.

Command \com{COMBINE} simplifies Data cube combinations, by combining individual steps that
are otherwise available in \qom{MAP\_REPROJECT, MAP\_RESAMPLE, MAP\_COMBINE}, 
while command \comm{VIEW}{/OVERLAY} allows visual comparison of two data cubes.


