How do I get statistics of an image or spectral cube?

It is useful to know the random noise level in your image before cleaning. You can calculate this directly using the Viewer via its Statistics panel as described below. The first method is the quickest and simplest, but if you wish to save the regions or the statistics, then we recommend you follow one of the other two approaches.

a) The simplest, interactive method uses the Viewer to obtain the statistics for an image.

$\parbox{0.7\textwidth}{ \small\begin{de... ...s details on how to use the {\bf Viewer}\vspace{-1.5\topsep}\end{description}}$

1. bring up a Viewer,

2. select $\Rightarrow$ desired channel (plane),

3. click on `Tools' on the top panel of the viewer, then click on `ImageAnalysis' -- an Image Analysis GUI should pop up,

4. in the Image Analysis GUI,
   pull down: statistics menu
   (by clicking on the triangle icon to the left).

5. Then either
   press the green Plane button to obtain the statistics within the entire image

   
   OR draw a region in the viewer and double click within it to obtain the statistics just within that region in that plane.

   
   

   
   

   $\parbox{0.7\textwidth}{ \small\begin{de... ... using the viewer, see Chapter \ref{vch}.\vspace{-1.5\topsep}\end{description}}$
   

The statistics including the rms will appear below the image in the statistics panel and the ``bounding box'' information is written to the Log Messages.

To obtain statistics in another part of the image, you may just resize the old box and move it to a new location. Double clicking inside the box will produce the statistics for this new region.

$\parbox{0.7\textwidth}{ \small\begin{description}\vspace{-1.5\topsep... ...me of the image and press the escape key.\vspace{-1.5\topsep}\end{description}}$

b) To be able to save the regions, begin by opening the regionmanager GUI.

$\parbox{0.7\textwidth}{ \small\begin{de... ... Chapter \ref{rch} (page \pageref{rch}).\vspace{-1.5\topsep}\end{description}}$

1. select $\Rightarrow$ desired image (e.g. co.image, under Images),

2. select $\Rightarrow$ interactive (under Region Types).

   
   This will bring up a Viewer

3. Now just follow the instructions in method a) above.

You get the same results in the statistics panel of the Viewer and in the Log Messages GUI. However, now `box' or `box1' and `intersection' should appear under the Name and Type columns in the regionmanager GUI and similarly under the Tools in Use GUI. You might have to press the Refresh button first to see them.

Subsequent regions will appear as box2, box3, etc. Refer to § 9.5 (page ) and § 9.10 (page ) to learn how to save and use these regions.

c) For more flexibility , select the statistics function of the imagetool.

$\parbox{0.7\textwidth}{ \small\begin{de... ...sis functions' --- click on \lq statistics.'\vspace{-1.5\topsep}\end{description}}$

Among the input parameters to fill in is region.

Either

• enter the name of the region

  
  

  
  

  $\parbox{0.9\textwidth}{ \small\begin{description}\vspace{-1.5\topsep... ...in Use view of the {\tt tool}manager GUI.\vspace{-1.5\topsep}\end{description}}$
  

or

• use the wrench to find other options, and

  
  

  
  

  $\parbox{0.9\textwidth}{ \small\begin{de... ...input parameter (page \pageref{awrench}).\vspace{-1.5\topsep}\end{description}}$
  

  
  

• press the Go button.

The statistics are written out in the statsout box at the bottom of the various input parameters of the Function: statistics.

The statistics are also nicely displayed in the Log Messages GUI, including the blc and trc of the bounding box (assuming you made a rectangular region).

If you selected ``from image'' from the wrench menu, then upon double clicking inside the region, the default name of the region, myregion, is entered for the region parameter in the Function: statistics as well as being added to the list of regions in the regionmanager GUI.

If you create a new box and double click within it, a new region called myregion1 will be created and recorded and once you press the Go button, the statistics will be recorded for that region.