Last modified: December 2014

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AHELP for CIAO 4.12 Sherpa v1


Context: filtering


Apply an include filter to all 2D datasets




The notice2d command specifies the region of 2D data to be included in the analysis. The filter is applied to all available dataset ids; to operate on specific ids, use the notice2d_id command.

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. 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 may need to be escaped: \" or \' . The symbols do not need to be escaped if they are in a region file.

If no filter is supplied, all data points in all datasets are included. Noticing the entire set is a method of clearing any filters that have been applied.

One-dimensional Data Filtering

To apply an include filter to 1D data, use the notice or the notice_id commands.


Example 1

sherpa> notice2d()

When the command is called without any filter, all data points in all sets are included.

Example 2

sherpa> notice2d("circle(275,275,50)")

A circular region defined in logical (image) coordinates is used to filter the data.

Example 3

sherpa> notice2d("box(3900.5,4120,189,188,0)+circle(4069,4250,20)")

Filter the data with a complex region (a rectangular plus a circle) in physical coordinates.

Example 4

sherpa> notice2d("/data/src.reg")

Filter the data with the region stored in /data/src.reg. In this case, it is a circular region defined in WCS decimal coordinates:

sherpa> !cat /data/src.reg
# Region file format: DS9 version 4.0
# Filename:

Example 5

sherpa> notice2d('circle(18:33:33.468,-10:34:08.66,42.6351")')
sherpa> notice2d('circle(18:33:33.468,-10:34:08.66,42.6351\")')
sherpa> notice2d("wcs.reg")

These commands are two equivalent ways of filtering the data with a region defined in WCS sexagesimal coordinates. The region file contains:

sherpa> !cat ~/src_wcs.reg

Note that the arcsec symbol (") may need to be escaped, dependin on whether the string is enclosed in single or double quotes.

Example 6

sherpa> notice2d("reg.fits")
sherpa> notice2d("region(reg.fits)")

These commands are two equivalent ways of filtering the data with a FITS region file. Generally, the regions should be defined in logical (image) coordinates.

unix% dmlist reg.fits blocks
Dataset: reg.fits
     Block Name                          Type         Dimensions
Block    1: PRIMARY                        Null        
Block    2: REGION                         Table         5 cols x 1        rows

unix% dmlist reg.fits data
Data for Table Block REGION
Region Block: Circle(1019,1060,20)
ROW    POS(X,Y)         SHAPE       R[2]      ROTANG[2]      COMPONENT
1      (1019.0, 1060.0) Circle      [20.0 0]  [0 0]          1


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

See Also

get_filter, ignore, ignore2d, ignore2d_id, ignore_bad, ignore_id, notice, notice2d_id, notice_id, show_filter