Chandra X-Ray Observatory
	(CXC)
Skip to the navigation links
Last modified: December 2013

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


AHELP for CIAO 4.6 Sherpa v2

get_int_proj

Context: confidence

Synopsis

Return the confidence data defining an interval projection plot

Syntax

get_int_proj( [par=None, id, otherids=None, recalc=False, min=None,
max=None, nloop=20, delv=None, fac=1, log=False,numcores] )

Description

The get_int_proj() function returns the data defining a confidence plot of fit statistic versus model parameter value for a single thawed model parameter, produced by the int_proj() function. (The parameter value is varied on the computed grid until the fit statistic is increased by delta_S, which is a function of sigma. For example, delta_S = 1 if the statistic is chi^2 and fac = 1 . All other thawed parameters are allowed to float to new best-fit values at each step, instead of being fixed to the initial best-fit values.)

The get_int_proj() function returns information on the most recent confidence plot produced with int_proj(), independent of the arguments supplied, unless the 'recalc' argument is set to True . For example, if an interval projection confidence plot is produced for the amplitude of a power law model, and then get_int_proj() is used to obtain confidence data on the gamma parameter of the power law model, the information returned by get_int_proj() will correspond to the confidence plot of the amplitude parameter, *unless* the 'recalc' argument is switched on.

The computationally intensive projection function is parallelized to make use of multi-core systems (i.e., laptops or desktops with 2 or 4 cores) to provide significant improvements in efficiency compared to previous releases of Sherpa; the 'numcores' argument may be used to specify how the cores should be used when projection is run.

  • par - source model parameter
  • id, otherids - the id(s) of the dataset(s) to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id"); otherids=None
  • recalc - re-calculate confidence data? ; default=False
  • min - minimum grid boundary; default=None, which calculates the value from the covariance. This is always a linear quantity, regardless of the log setting.
  • max - maximum grid boundary; default=None, which calculates the value from the covariance. This is always a linear quantity, regardless of the log setting.
  • nloop - bin size for calculating the step size (delv); default=20
  • delv - step size; default=None, which calculates the value using the min, max, and nloop values
  • fac - the number of sigma (i.e., the change in statistic) for the plot; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id")
  • log - use log space for the grid interval? default=False
  • numcores - number of cores to use in parallelization; default is to use all cores available (2 or 4)

Example 1

sherpa> print(get_int_proj())

When called with no arguments from within the print command, get_int_proj() returns the confidence data defining the most recently produced interval projection plot.

Example 2

sherpa> print(get_int_proj("p1.gamma", id=2, recalc=True))

This command will calculate and return the interval projection confidence data for the gamma parameter of power law model 'p1', which is assigned to data set 2.

sherpa> print(get_int_proj("p1.gamma", id=2, recalc=True))

x     = [-10.      -8.9474  -7.8947 ...,   7.8947   8.9474  10.    ]
y     = [ 436.2093  436.3852  436.0802 ...,  442.5094  443.0242  443.3257]
min   = -10.0
max   = 10.0
nloop = 20
delv  = None
fac   = 1
log   = False

Bugs

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

See Also

confidence
conf, covariance, get_conf, get_covar, get_int_unc, get_proj, get_reg_proj, get_reg_unc, int_proj, int_unc, projection, reg_proj, reg_unc, set_conf_opt, set_covar_opt, set_proj_opt
contrib
get_chart_spectrum
data
get_areascal, get_arf, get_arf_plot, get_axes, get_backscal, get_bkg, get_bkg_plot, get_bkg_scale, get_coord, get_counts, get_data, get_data_plot, get_dep, get_dims, get_error, get_exposure, get_grouping, get_indep, get_quality, get_rmf, get_specresp, get_staterror, get_syserror
filtering
get_filter
fitting
calc_stat_info, get_fit, get_stat_info
info
get_default_id, list_stats
methods
get_draws, get_iter_method_name, get_iter_method_opt, get_method
modeling
get_model, get_model_component, get_model_component_image, get_model_component_plot, get_model_plot, get_num_par, get_order_plot, get_par, get_pileup_model, get_response, get_source, get_source_component_image, get_source_component_plot, image_source
plotting
get_split_plot
psfs
get_kernel, get_psf
statistics
get_chisqr_plot, get_delchi_plot, get_prior, get_sampler, get_stat
utilities
get_analysis, get_rate
visualization
get_ratio, get_resid, image_getregion

Last modified: December 2013
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:   cxcweb@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2014. All rights reserved.