Chandra X-Ray Observatory
	(CXC)
Skip to the navigation links
Last modified: December 2014

URL: http://cxc.harvard.edu/sherpa/ahelp/load_data.html
Jump to: Description · Examples · Bugs · See Also


AHELP for CIAO 4.9 Sherpa v1

load_data

Context: data

Synopsis

Load 1D data from a file

Syntax

load_data( [id], filename, [options] )

Description

The load_data command is a filetype-independent method of loading 1D data from a file (e.g. if the file-specific load command is unknown or if the filetype is unknown). It tries to load the file in the following order: load_pha, load_table, and 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 - the name of the file (with path) which contains the data

If the filetype is known, file-specific options may be included in the load_data command. They are:

  • load_pha: use_errors
  • load_table: ncols, colkeys, and dstype
  • load_ascii: ncols, colkeys, sep, comment, and dstype

Refer to the individual command ahelp files for specifics on the options.

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_data("data.filtered")

Using the default settings, load a data file into Sherpa.

Example 2

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

Load the first three columns of data.txt, using the dataset id "src". This example could also have been done using the load_ascii command.

Example 3

sherpa> load_data("src", "source.pha")

Data is loaded from the file source.pha with data id "src". This example could also have been done using the load_pha command.

Example 4

sherpa> load_data("rprofile_mid.fits[cols RMID,SUR_BRI,SUR_BRI_ERR]")
sherpa> load_data("rprofile_mid.fits",
colkeys=["RMID","SUR_BRI","SUR_BRI_ERR"])

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. This example could also have been done using the load_table command.

Example 5

sherpa> load_data("test_data.dat", dstype=Data1DInt)
sherpa> load_data("test_data.dat[opt colnames=first]", dstype=Data1DInt)
sherpa> load_data("test_data.dat[cols xlo,xhi,y,staterror]",
dstype=Data1DInt)

This example shows three equivalent ways of loading four columns named 'xlo','xhi','y', and 'staterror' from the ASCII file test_data.dat, where the latter uses the CIAO Data Model ASCII kernel to select the desired columns.

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_ascii, load_bkg, load_bkg_arf, load_bkg_rmf, 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
Smithsonian Institute Smithsonian Institute

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email:   cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2017. All rights reserved.