link

Synopsis

Link a model parameter to another model parameter.

link( par, val )

Description

The link command links model parameters together, so that the value of one model parameter is determined by the value of another model parameter. The model parameter being linked may be set to an arbitrary arithmetic expression that includes the other model parameter. The linked parameters may be thawed or frozen during the fit with commands thaw() and freeze(), and can be unlinked with the command unlink().

• par - Sherpa model parameter to be linked
• val - value of other model parameter or arithmetic function of other model parameter, assigned to 'par'

Example 1

sherpa> link(p1.phoindex, p1.norm)

The link() function assigns the value of the second argument to the first argument. Here, the 'phoindex' parameter of model "p1" is set to the value of the 'norm' parameter of the same model.

Example 2

sherpa> link(p1.phoindex, 1.7*p1.norm)

In this example, the value of the 'phoindex' parameter of model "p1" is set to the 'norm' parameter value multiplied by 1.7.

Example 3

The changes made by the link() function can be viewed with show_model():

sherpa> show_model()
(xsphabs.abs1 * xspowerlaw.p1)
Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   abs1.nh      frozen         0.03            0        1e+05 10^22 atoms / cm^2
   p1.phoindex  thawed          1.7           -2            9           
   p1.norm      thawed            1            0        1e+24   

sherpa> link(p1.phoindex, p1.norm)

sherpa> show_model()
(xsphabs.abs1 * xspowerlaw.p1)
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   abs1.nh      frozen         0.03            0        1e+05 10^22 atoms / cm^2
   p1.phoindex  linked            1            expr: p1.norm           
   p1.norm      thawed            1            0        1e+24           
          

Bugs

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

See Also

data

get_bkg_plot

info

list_model_ids, show_bkg_model, show_bkg_source

modeling

add_model, add_user_pars, clean, create_model_component, delete_bkg_model, delete_model, delete_model_component, freeze, get_model, get_model_autoassign_func, 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_source, get_source_component_image, get_source_component_plot, guess, image_model, image_model_component, image_source, image_source_component, integrate, integrate1d, load_table_model, load_template_model, load_user_model, normal_sample, paramprompt, reset, save_model, save_source, set_bkg_model, set_full_model, set_model_autoassign_func, set_par, set_pileup_model, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset, t_sample, thaw, uniform_sample, unlink

plotting

get_lrt_plot, get_lrt_results, get_pvalue_plot, get_pvalue_results, plot_cdf, plot_lrt, plot_model, plot_model_component, plot_pdf, plot_pvalue, plot_scatter, plot_source, plot_source_component, plot_trace

psfs

delete_psf, load_conv

saving

save_delchi, save_resid

utilities

calc_chisqr, calc_energy_flux, calc_model_sum, calc_photon_flux, calc_source_sum, calc_stat, eqwidth

visualization

contour_model, contour_ratio, contour_resid, get_ratio, get_resid