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Last modified: 21 September 2010

URL: http://cxc-newtest.cfa.harvard.edu/ciao4.2/bugs/regions.html

Bugs: regions


Caveats

  1. CIAO does not understand the format ds9 uses for writing elliptical annuli or for writing grids of annuli.

Bugs

  1. World-coordinate region filters don't work correctly if the EQPOS transform includes a rotation.

  2. Regions off the image: the Data Model crashes when filtering a region that's completely off the image.

  3. Using incorrect syntax with the rectangle shape does not fail when filtering.

  4. If you spatially filter a file with a complicated region and then supply the same region later in the analysis, the second filter may not be applied correctly.

  5. Combining region and range filters.

  6. If the angle of a pie region crosses 360 degrees, the modulo 360 is not correctly taken into account. (02 Mar 2010)


Caveats

  1. CIAO does not understand the format ds9 uses for writing elliptical annuli or for writing grids of annuli.


Bugs

  1. World-coordinate region filters don't work correctly if the EQPOS transform includes a rotation.

    The rotation is not applied when converting the region from world to physical coordinates. In this case, region filters should be written only in terms of physical coordinates (i.e. SKY pixels).

  2. Regions off the image: the Data Model crashes when filtering a region that's completely off the image.

  3. Using incorrect syntax with the rectangle shape does not fail when filtering.

    For example, setting xmax > xmin and/or ymax > ymin. Instead it appears that the Data Model simply swaps the min and max values.

  4. If you spatially filter a file with a complicated region and then supply the same region later in the analysis, the second filter may not be applied correctly.

    For example:

    unix% dmcopy evt.fits[sky=region(complex.reg)][bin sky=1] out.fits
    unix% dmstat out.fits[sky=region(complex.reg)] cen-
    

    This is due to the fact that the regions applied in the dmcopy are recorded in the file subspace, and the subsequent tool - dmstat in this case - does not combine them with the second (identical) filter correctly. Other tools that take the subspace into account will exhibit this problem as well.

    The example does work for simple regions, e.g. "circle(4096,4096,10)", but the workarounds can still be applied.

    Workarounds:

    1. Use "[opt update=no]" in the dmcopy step so that the filter does not get recorded in the subspace. Be aware, however, that this means you lose information on what filters have been applied to the data.

    2. omit the DM filter from the second infile name.

  5. Combining region and range filters.

    This command:

    unix% dmcopy "input.fits[sky=circle(4096,4096,100),y=4020:4100,4250,4350]" \
          output.fits
    

    fails to do the y filter altogether. This bug also applies to exclude filters.

  6. If the angle of a pie region crosses 360 degrees, the modulo 360 is not correctly taken into account. (02 Mar 2010)

    Compare the output of these two commands:

    % dmstat "file.fits[sky=pie(03:19:48.390,+41:30:41.42,8.5',9',350,366)]" centroid=no
    EVENTS_IMAGE
        min: 1 @: ( 4759 3089 )
        max: 1 @: ( 4759 3089 )
       mean: 1
        sum: 4538
       good: 4538
       null: 1202164
    
    % dmstat "file.fits[sky=pie(03:19:48.390,+41:30:41.42,8.5',9',100,116)]" centroid=no
    EVENTS_IMAGE
        min: 1 @: ( 3233 4211 )
        max: 1 @: ( 3233 4211 )
       mean: 1
        sum: 4538
       good: 4538
       null: 7014
    

    When computing the bounds of the 350:366 pie, the modulo 360 is not correctly taken into account.

    Workaround:

    Modify the pie region by 360 degrees manually before running the command:

    % dmstat "file.fits[sky=pie(03:19:48.390,+41:30:41.42,8.5',9',350,6)]" centroid=no
    EVENTS_IMAGE
        min: 1 @: ( 4759 3089 )
        max: 1 @: ( 4759 3089 )
       mean: 1
        sum: 4538
       good: 4538
       null: 1622
    

Last modified: 21 September 2010