I/O Bugs: general

Caveats

1. If the boundaries of a bin (e.g. 20 to 25) are partially included in a filter interval (e.g. 24 to 26), the entire bin is retained in the output.

Bugs

1. When working in WCS coordinates, a region file may be applied incorrectly to the data in Sherpa.

2. Attempts to input data from directories other than the present working directory may fail.

3. Filter commands with extra extraneous characters are applied successfully, although it causes a parse error.

4. If a 2-D filter is assigned to Sherpa via the Sherpa/S-Lang module command set_filter(), and subsequently the command SAVE ALL is issued, then no information about the filter is saved.

5. Actions (e.g. defining filters) using regions with quantities in arcseconds will fail.

6. Applying the same (2-D) region filter to source and background data yields an "Illegal instruction".

Caveats

1. If the boundaries of a bin (e.g. 20 to 25) are partially included in a filter interval (e.g. 24 to 26), the entire bin is retained in the output.

   For instance, using this sample data:

   [17.500000] = 0.186
   [22.500000] = 0.1487
   [27.500000] = 0.1209
   

   Note that Sherpa uses the center of the bin as its nominal position. When Sherpa interprets the filter ignore filter 24:28, there is only one bin in the above list that falls in that interval: bin 5, with a position of 27.5. In the case of the filter ignore filter 24:26, both bin 4 (position of 22.5) and bin 5 (position of 27.5) are selected.

   In both cases there are counts from bin 4 and bin 5 that fall within the interval indicated by the filter. Since the filter only overlaps part of the bin, Sherpa keeps the entire bin. This allows the user to look at the results and modify the filter to include (or exclude) more points if desired.

Bugs

1. When working in WCS coordinates, a region file may be applied incorrectly to the data in Sherpa.

   Regions can be saved from ds9 to file, and later read into Sherpa so that regions can be noticed or ignored (e.g., with "notice filter \"region(foo.reg)\"", where foo.reg was saved from an earlier ds9 session). When working in WCS coordinates, a region file may be applied incorrectly; it is better to work in image coordinates if possible.

2. Attempts to input data from directories other than the present working directory may fail.

   Workaround:

   delimit the input filename with quotes:

   sherpa> data ../img.fits
   Syntax Error: data ../img.fits;
   sherpa> data "../img.fits"
   sherpa>
   

3. Filter commands with extra extraneous characters are applied successfully, although it causes a parse error.

   sherpa> notice filter 10:30 foofoofoo
   Parse Error/Undefined Name: notice filter 10:30 foofoofoo;
   sherpa> show
   ...
   Current filters for dataset 1:
   notice source 1 filter 10 : 30 foofoofoo 
   Noticed filter size: 21 bins 
   ...
   

   The filter is applied, but cannot be successfully read back in if saved.

4. If a 2-D filter is assigned to Sherpa via the Sherpa/S-Lang module command set_filter(), and subsequently the command SAVE ALL is issued, then no information about the filter is saved.

   This is because the shape or source cannot be rendered in a line of text. One possible solution for this in future versions of Sherpa is to write out the filter to disk, and SAVE a READ FILTER command expression.

5. Actions (e.g. defining filters) using regions with quantities in arcseconds will fail.

   For example:

   sherpa> notice world "ellipse(325,-23,9.9",8.2",94)"
   

   will not work because of the extra quote marks.

   Workaround:

   convert the quantities to arcminutes.

6. Applying the same (2-D) region filter to source and background data yields an "Illegal instruction".

   sherpa> data "img_bin8_7_70.fits[440:600,392:557]" fits
   sherpa> read back "smbg_bin8_7_70.fits[440:600,392:557]" fits
   sherpa> notice filter "circle(80,90,26)"
   sherpa> quit
   Goodbye.
   Illegal instruction
   

   Workaround:

   specify the filter twice:

   sherpa> data "img_bin8_7_70.fits[440:600,392:557]" fits
   sherpa> read back "smbg_bin8_7_70.fits[440:600,392:557]" fits
   sherpa> notice source filter "circle(80,90,26)"
   sherpa> notice back filter "circle(80,90,26)"  
   sherpa> quit
   Goodbye.