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Last modified: December 2013

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AHELP for CIAO 4.9 Sherpa v1


Context: filtering


Apply an exclude region filter to 2-D data by data set ID(s).


ignore2d_id( ids, [val] )


Specifies a region mask to be excluded from 2-D data by data set ID, using CIAO region syntax or a region file.

  • id - the id(s) of the data set(s) to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id")
  • val - a filter defined by CIAO region syntax or a FITS or ASCII region filename (including path); default=None

The filter must be defined in the same coordinate system as the "coord" field of the data structure, which is returned by the get_coord command ("ahelp get_coord"). For information on the CIAO region filtering syntax, refer to "ahelp dmregions".

If the region definition on the Sherpa command line contains an arcsec or arcmin symbol, it must be escaped: \" or \' . The symbols do not need to be escaped if they are in a region file.

One-dimensional Data Filtering

To apply an exclude filter to 1-D data, use the ignore command ("ahelp ignore") or the ignore_id command ("ahelp ignore_id").

Example 1

sherpa> ignore2d_id()

When the function ignore2d_id is called with no arguments, the filter will ignore all data points on the grid of the default data set ID.

Example 2

sherpa> ignore2d_id(3, "circle(25,25,5)")
sherpa> ignore2d_id(3, "circle(259.18823,67.14189,0.01)")

Supplying a region string in CIAO region syntax, such as "circle(x_center, y_center, radius)" in physical coordinates, will apply the filter to the supplied data set ID(s). Here, a circular region is excluded from data set "3".

Example 3

sherpa> ignore2d_id([2,4], "circle(4300,3710,15)")

A circular region is excluded from data sets "2" and "4".

Example 4

sherpa> !cat filter.reg
sherpa> ignore2d_id("psf", "filter.reg")

The ASCII region file filter.reg is used to filter the image. In this case we exclude all pixels within the circle centered at 4070,3940 and with a radius of 6. The data set specified in this example is "psf".


See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

get_filter, ignore, ignore2d, ignore_bad, ignore_id, notice, notice2d, notice2d_id, notice_id, show_filter

Last modified: December 2013
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