Name
average - cube averaging
Synopsis
average [options] [parameters]
Description
average reduces a FITS cube over its third dimension, by
applying one of several possible algorithms described
below. Users should specify a cut and a method. The cut
describes how planes in the input cube are grouped for
averaging, the method specifies what kind of average is
applied.
Parameters
-i <incube> or --in <incube>
Specifies the name of the input cube (mandatory).
-o <outcube> or --out <outcube>
Specifies the name of the output cube (optional).
Default output name for an input cube named
incube.fits is incube.avg.fits.
Options
Cuts
Cuts specify how to group the input planes to apply the
average. Default cut is --cut whole.
--cut whole
applies the average on the whole cube, i.e. all
planes are averaged to a single one according to
the requested method.
--cut cycle --step <n>
applies the average for every <n> planes in the
input cube. For example, if the input cube contains
50 planes and this cut is specified with n=10, the
planes will be averaged 10 by 10 to produce one
cube in output containing 5 planes.
--cut running --halfwidth <h>
Performs a running average: the output is a cube
containing as many planes as the input cube. Each
plane is the result of an average over an interval
centered on the same plane in the input, plus or
minus <h> planes. This means that central planes
will be the average of 2h+1 input planes, and edge
planes will be an average of between h+1 and 2h+1
input planes.
Example: the input cube has 6 planes, h=2. Brackets show
where the central plane is at each iteration.
plane 1 is built from [1] 2 3
plane 2 is built from 1 [2] 3 4
plane 3 is built from 1 2 [3] 4 5
plane 4 is built from 2 3 [4] 5 6
plane 5 is built from 3 4 [5] 6
plane 6 is built from 4 5 [6]
Methods
Methods specify how to perform the average. Default is
linear.
--method linear
Performs a normal, linear average of the input
planes.
--method sum
Same as linear, but does not divide by the number
of averaged planes at the end. Useful for cubes
which do not have much signal.
--method median
Median filtering along the z-axis.
--method filtered
with additional parameters --filt-low npix and
--filt-high npix. This is actually an extension of
the median average. A time line is extracted for
each pixel position on the detector (along the z-
axis), and then sorted out. The median average
would only keep the central value, whereas this
method requests two numbers specifying how many low
and high pixels shall be rejected before making an
average.
Files
Input files shall all comply with FITS format.
Bugs
It is not yet possible to combine a running filter cut
with a filtered average method.