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

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

Besides generic data cube handling tools, \imager{} offers more
specific tools are particularly useful for weak signal detection.
Some of them are generic (source agnostic, such as the Matched Filtering), 
others specific of some astrophysical situations (e.g. the \qom{KEPLER} 
tool that applies to any rotating structure with azimutal symmetry).

\subsection{Basic Data Cube Handling and Comparison}

The  \qom{MAP\_*} suite of commands (\com{MAP\_COMBINE}, \com{MAP\_COMPRESS}, \com{MAP\_INTEGRATE}
\com{MAP\_REPROJECT}, \com{MAP\_RESAMPLE}, \com{MAP\_SMOOTH} and \com{MAP\_CONVOLVE}
allow basic operations on Data Cubes: combinations, rotation, spatial and spectral
resampling, comparisons.

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.

\com{MAP\_CONTINUUM} allows extraction of the continuum emission from spectral
line data cubes, trying to avoid as much as possible line contamination
in a spatially dependent (or independent) way.

\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 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 if the
rotation curve is known.


