Last modified: June 2019

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AHELP for CIAO 4.16 Sherpa


Context: contrib


Return the data used to create the radial or elliptical profile of the residuals (data - model)/error to imaging data.


get_delchi_prof( [id], [model=None, rstep=None, rmin=None, rmax=None,
rlo=None, rhi=None, xpos=None, ypos=None, ellip=None, theta=None,
group_counts=None, group_snr=None, recalc=True] )


The get_delchi_prof() command calculates the radial - or elliptical - profile of the residuals to imaging data and returns an object containing the values. The profile is defined by the existing model compenents, although it is possible to over-ride these values.

The residual values are calculated as

(data - model) / error

The get_resid_prof() command can be used if you want to use

data - model

Loading the routine

The routine can be loaded into Sherpa by saying:

from sherpa_contrib.profiles import *

Argument options

The argument options are the same as for the prof_delchi() command - except that the label and overplot arguments are not supported - and are described in its ahelp page.

Fields returned by get_delchi_prof

The following table lists the fields in the object returned by the get_delchi_prof() command. These values can also be seen by using the print command on the object:

sherpa> d = get_delchi_prof(rstep=10)
sherpa> print (d)
Field name Description
xlo The lower-limits of the radial bins
xhi The upper-limits of the radial bins
y The calculated profile value; sum of (data - model) / area
yerr The error on y
xlabel The label for the X axis
ylabel The label for the Y axis
labels The labels giving the profile parameters
title The plot title
histo_prefs The preferences for the plot


Example 1

sherpa> d10 = get_delchi_prof(group_snr=10)
sherpa> d20 = get_delchi_prof(group_snr=20)

Two profiles of the same dataset are calculated; d10 uses a signal-to-noise ratio of 10 and d20 a value of 20.

Example 2

sherpa> prof_delchi("src1", group_counts=100)
sherpa> da = get_delchi_prof(recalc=False)
sherpa> prof_delchi("src2", rlo=da.xlo, rhi=da.xhi, overplot=True)

A profile is calculated and displayed for the dataset "src1". The bin edges from this are then used to create a profile for the dataset "src2", which is overlain on the first plot. Note that recalc is set to False in the call to get_delchi_prof() to avoid unnescessary re-calculations.


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

See Also

get_data_prof, get_data_prof_prefs, get_delchi_prof_prefs, get_fit_prof, get_model_prof, get_model_prof_prefs, get_resid_prof, get_resid_prof_prefs, get_source_prof, get_source_prof_prefs, plot_chart_spectrum, plot_marx_spectrum, prof_data, prof_delchi, prof_fit, prof_fit_delchi, prof_fit_resid, prof_model, prof_resid, prof_source, sherpa_profiles
get_arf_plot, get_bkg_chisqr_plot, get_bkg_delchi_plot, get_bkg_fit_plot, get_bkg_model_plot, get_bkg_plot, get_bkg_ratio_plot, get_bkg_resid_plot, get_bkg_source_plot
normal_sample, t_sample, uniform_sample
get_cdf_plot, get_energy_flux_hist, get_pdf_plot, get_photon_flux_hist, get_pvalue_plot, get_pvalue_results, get_split_plot, plot, plot_arf, plot_bkg, plot_bkg_chisqr, plot_bkg_delchi, plot_bkg_fit, plot_bkg_fit_delchi, plot_bkg_fit_resid, plot_bkg_model, plot_bkg_ratio, plot_bkg_resid, plot_bkg_source, plot_cdf, plot_chisqr, plot_data, plot_delchi, plot_energy_flux, plot_fit, plot_fit_delchi, plot_fit_resid, plot_model, plot_model_component, plot_order, plot_pdf, plot_photon_flux, plot_pvalue, plot_ratio, plot_resid, plot_scatter, plot_source, plot_source_component, plot_trace, set_xlinear, set_xlog, set_ylinear, set_ylog
get_chisqr_plot, get_delchi_plot