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Last modified: December 2014

URL: http://cxc.harvard.edu/sherpa/ahelp/load_ascii.html
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AHELP for CIAO 4.9 Sherpa v1

load_ascii

Context: data

Synopsis

Load ASCII data

Syntax

load_ascii( [id], filename, [ncols=2, colkeys=None, sep=" ",
comment='#', dstype=Data1D] )

Description

The load_ascii command loads ASCII data from a column-based text file.

  • 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 - the name of the file (with path) which contains the data
  • ncols - number of columns to read; default=2
  • colkeys - list of column names; default=None
  • sep - the column-separating character; default is a space (" ")
  • comment - character which indicates a comment line; default=#
  • dstype - dataset type: Data1D, Data1DInt, Data2D, Data2DInt; default=Data1D

For more information on working with ASCII files in CIAO, refer to "ahelp dmascii".

The columns to load are specified by a Data Model filter on the filename or the colkeys option of the load_ascii 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_ascii 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).

Loading Multiple Data Sets

Multiple data sets can be loaded using the datastack syntax, where 'id' is replaced by the datastack identifier ('[]' as default) and the list of data sets is contained in the filename and input as "@filename", e.g. load_*([],'@filename'). See 'datastack' ahelp file for the full description.

Example 1

sherpa> load_ascii("src", "data.txt", ncols=3)

Load the first three columns of data.txt, using the dataset id "src".

Example 2

sherpa> load_ascii("tabbed.txt", sep="\t")

Load ASCII data from tabbed.txt, which uses a tab as the separator character.

Example 3

sherpa> load_ascii("radpro.txt[cols RMID, SUR_BRI, SUR_BRI_ERR]",
dstype=Data1D)
sherpa> load_ascii("radpro.txt", colkeys=["RMID", "SUR_BRI",
"SUR_BRI_ERR"], dstype=Data1D)

The two commands are equivalent. The columns RMID, SUR_BRI, and SUR_BRI_ERR correspond to the x, y, and staterror columns in the Data1D dataset radpro.txt:

sherpa> !cat radpro.txt
#SUR_BRI SUR_BRI_ERR RMID
3.4 0.4 1
3.5 0.4 2
3.6 0.4 3 
...

The default comment character and column separator are used.

Example 4

sherpa> load_ascii("binned.txt[cols LO, HI, Y, ERR]", dstype=Data1DInt)
sherpa> load_ascii("binned.txt", colkeys=["LO", "HI", "Y", "ERR"],
dstype=Data1DInt)

The two commands are equivalent ways of loading an ASCII dataset in which the independent grid is binned.

sherpa> !cat binned.txt
#LO HI Y ERR
0.1 0.2 3.5 0.4
0.2 0.3 3.6 0.4
0.3 0.4 3.7 0.4 
...

Bugs

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

See Also

data
copy_data, dataspace1d, dataspace2d, datastack, delete_data, fake, get_axes, get_bkg_plot, get_counts, get_data, get_data_plot, get_dep, get_dims, get_error, get_quality, get_specresp, get_staterror, get_syserror, group, load_arf, load_arrays, 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, set_data, set_quality, ungroup, unpack_arf, unpack_arrays, unpack_ascii, unpack_bkg, unpack_data, unpack_image, unpack_pha, unpack_rmf, unpack_table
filtering
get_filter, load_filter, set_filter
info
get_default_id, list_bkg_ids, list_data_ids, list_response_ids
modeling
add_model, add_user_pars, clean, load_table_model, load_template_model, load_user_model, save_model, save_source
plotting
plot_data, set_xlinear, set_xlog, set_ylinear, set_ylog
saving
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
statistics
load_user_stat
utilities
calc_data_sum, calc_data_sum2d, calc_ftest, calc_kcorr, calc_mlr, calc_model_sum2d, calc_source_sum2d, get_rate
visualization
contour, contour_data, contour_ratio, get_ratio, get_resid, histogram1d, histogram2d, image_data, rebin

Last modified: December 2014
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