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Last modified: December 2010

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AHELP for CIAO 4.3 Sherpa v1


Context: data


Load tabular data


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


The load_table command loads tabular data from a FITS table, a column-based text file, or a TABLECrate object.

The load_ascii command is similar to load_table, but allows the user to specify the comment character and column separator used in the input file ("ahelp load_ascii").

  • id - the id of the dataset to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id")
  • 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 load_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

While possible, it is not recommended that load_table be used with images (2D dstypes), PHA files, or ARF and RMF response files. For these cases, use the load command specific to the filetype instead (e.g. load_image).

Example 1

sherpa> load_table("rprofile_mid.fits[cols RMID,SUR_BRI,SUR_BRI_ERR]")
sherpa> load_table("rprofile_mid.fits",

These commands are equivalent ways of loading x=RMID, y=SUR_BRI, and staterror=SUR_BRI_ERR from rprofile_mid.fits, a radial profile for which the midpoint of the annular regions has been calculated.

Example 2

sherpa> load_table("rprof", "rprofile.fits[cols
R,SUR_BRI,SUR_BRI_ERR]", dstype=Data1DInt)
sherpa> load_table("rprof", "rprofile.fits",
colkeys=["R","SUR_BRI","SUR_BRI_ERR"], dstype=Data1DInt)

Two ways of loading a radial profile as dataset id "rprof". The Data1DInt dstype is used in this example so that the column R, a vector column containing the annulus radii, is loaded as xlo=R[0], xhi=R[1]; the remaining columns are y=SUR_BRI, and staterror=SUR_BRI_ERR.

Example 3

sherpa> load_table(1, "tbl.fits", colkeys=["x", "y", "net_error"])

Three columns are read from the file tbl.fits.

Example 4

sherpa> load_table(2, "input.dat", ncols=2, colkeys=["col1", "col5"])

Columns "col1" and "col5" are read from the file input.dat and assigned as dataset id 2.

Example 5

sherpa> tabcr = read_file("")
sherpa> load_table(tabcr)

Tabular data is read into a TABLECrate (named "tabcr") from The table is then loaded into Sherpa from the crate, using the default options.


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, pack_image, pack_pha, pack_table, unpack_arf, unpack_arrays, unpack_ascii, unpack_bkg, unpack_data, unpack_image, unpack_pha, unpack_rmf, unpack_table
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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