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Last modified: December 2010

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AHELP for CIAO 4.3 Sherpa v1


Context: data


Unpack tabular data from a TABLECrate


unpack_table( filename|TABLECrate, [ncols=2, colkeys=None,
dstype=Data1D] )


The unpack_table command unpacks tabular data from a FITS file, a column-based text file, or a TABLECrate object into a Sherpa data object.

If a filename is provided as input, a crate is created but hidden and cannot be used for other analysis in the session.

  • filename|TABLECrate - the name of the file (with path) or TABLECrate which contains the data
  • ncols - number of columns to read; default=2
  • colkeys - list of column names; default=None
  • dstype - dataset type: Data1D, Data1DInt, Data2D, Data2DInt; default=Data1D

The columns to load are specified by a Data Model filter on the filename or the colkeys option of the unpack_table command, as shown in the examples. Vector columns are separated to form two dstype columns when the file is loaded. If no columns are specified, the first two columns in the file are read by default. If column names are not included in the file, Sherpa calls them "col1", "col2", etc.

The columns must be listed in the order required by the dataset type:

  • Data1D: x, y, staterror=None, syserror=None
  • Data1DInt: xlo, xhi, y, staterror=None, syserror=None
  • Data2D: x0, x1, y, shape=None, staterror=None, syserror=None
  • Data2DInt: x0lo, x1lo, x0hi, x1hi, y, shape=None, staterror=None, syserror=None

Example 1

sherpa> rprof = unpack_table("rprofile_mid.fits[cols
sherpa> rprof = unpack_table("rprofile_mid.fits",

These commands are equivalent ways of creating a data object called "rprof" from the RMID, SUR_BRI, and SUR_BRI_ERR columns of rprofile_mid.fits, a radial profile for which the midpoint of the annular regions has been calculated.

Example 2

sherpa> tabcr = read_file("")
sherpa> tabdat = unpack_table(tabcr)

Tabular data is read into a TABLECrate (named "tabcr") from The data is then unpacked into Sherpa from the crate.


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

See Also

dataspace1d, dataspace2d, fake, load_arf, load_arrays, load_ascii, load_bkg, load_bkg_arf, load_bkg_rmf, load_data, load_grouping, load_image, load_multi_arfs, load_multi_rmfs, load_pha, load_quality, load_rmf, load_staterror, load_syserror, load_table, pack_image, pack_pha, pack_table, unpack_arf, unpack_arrays, unpack_ascii, unpack_bkg, unpack_data, unpack_image, unpack_pha, unpack_rmf
get_default_id, list_bkg_ids, list_data_ids
add_model, add_user_pars, load_table_model, load_user_model, save_model, save_source
save_arrays, save_data, save_delchi, save_error, save_filter, save_grouping, save_image, save_pha, save_quality, save_resid, save_staterror, save_syserror, save_table

Last modified: December 2010
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