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Basic Information on contsub
Purpose: Subtract continuum from a datacube
Categories: map manipulation
CONTSUB is used to subtract the continuum from a datacube which
can be arbitrarily oriented. Several subtraction algorithms are
possible, selected using the mode keyword. The maximum length
of the spectral axis is 8192 pixels.
Standard keyword in. See the help on in for more information.
Standard keyword region. See the help on region for more information.
Anything outside the region is untouched (only rectangular boxes
are recognized by contsub).
Standard keyword out. See the help on out for more information.
For modes poly, mean and avgs either this keyword or cont= must
be specified, for mode subtr it must always be given. This
output dataset will contain only those channels from the input
dataset selected by the 'region' keyword.
An optional output dataset which will be one plane deep and
contain the continuum map. For mode=
poly: the interpolated map at the channel halfway between the
first and last line channel selected.
mean: the averaged image that was subtracted from the channel
avgs: the average of the two average images that are
calculated (see description of mode keyword).
subtr: an input set which will be subtracted from each plane
of the input dataset.
For modes poly, mean and avgs either this keyword or out= must
be specified, while for mode subtr it must always be given.
Select channels that supposedly contain continuum signal only.
A selection is a list of ranges. A range is specified as
(z1,z2), meaning channels z1 through z2, or as (z3) for a single
channel. Ranges are separated by commas, e.g.
For options 'poly' (or 'mean'), the fit (or average), is done
using all selected continuum channels. For option 'avgs', the
selection of continuum channels must consist of two ranges.
The 'contchan' keyword always refers to spectral channels,
independent of whether the spectral axis is the 'z'-axis, the
'x'-axis or any other axis.
(Not used for mode='subtr').
Selects the continuum-determination algorithm. In each case the
operation is done separately for each image pixel. May be
abbreviated. The default is 'poly,1'.
'poly,#' - a polynomial fit of order # is made through the
selected continuum channels. The interpolated continuum
intensity is subtracted from each separate channels. The
maximum order is 8.
'mean' - the average intensity of the selected continuum
channels is calculated and the average is subtracted from each
channel (equivalent to 'poly,0').
'avgs' - an average of the first range and of the second range
of channels is calculated and a linear interpolation between the
two averages is subtracted from each channel.
'subtr' - at each position, subtract the value in the dataset
given by cont= from the profile at the same position in the
Select which output to write with the cont keyword. By default
the continuum is written. If options=coeff,# one of the
coefficients of the polynomial fit is written instead.
'#' gives the order for which the coefficient is written (e.g.
if cont=a+bx: 0='a', 1='b', etc).
verbose=true makes contsub print out some info every now and
For datacubes where the spectral axis cannot be determined
automatically, this may be used to indicate which it is. Must
be one of 'x', 'y', 'z', 'a', 'b', 'c', or 'd'.
The default is 'z'.
Revision: 1.5, 2012/03/13 02:21:33 UTC
Generated by email@example.com on 21 Jun 2016