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 aver-
aged 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 cen-
tral 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 sig-
nal.
--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.