About Chandra Archive Proposer Instruments & Calibration Newsletters Data Analysis HelpDesk Calibration Database NASA Archives & Centers Chandra Science Links

Skip the navigation links
Last modified: December 2008

URL: http://cxc.harvard.edu/sherpa4.1/add_user_pars.sl.html
AHELP for Sherpa 4.1

add_user_pars

Context: sl.sherpa

Synopsis

Add parameters to a user-defined model

Syntax

add_user_pars( modelname, parnames; [parvals, parmins, parmaxs,
parunits, parfrozen] );

Description

The add_user_pars command sets up a user-defined model with parameter values which can be use in model definitions. Refer to the load_user_model help file for information on creating a model ("ahelp load_user_model") .

Note that all the parameters must be defined at the same time by add_user_pars. Each time the command is run, it overwrites any previously-defined parameters for the model.

  • modelname - the name of the model to which the parameters should be added
  • parnames - list of names for the new parameters ; default=NULL
  • parvals - list of parameter values; default=0
  • parmins - list of minimum values for the parameter ; default=-3.40282e+38
  • parmaxs - list of maximum values for the parameter ; default=3.40282e+38
  • parunits - list of parameter units; default=NULL
  • parfrozen - list of whether the parameters are frozen; default=0 (the parameter is thawed)

The parameters must be specified in the order that the function expects. That is, if the function has two parameters, pars[0]=slope and pars[1]=y-intercept, then the call to "add_user_pars" must be ["slope", "yint"] (and not ["yint", "slope"]).

More information on creating custom models is available on the Sherpa website.

Example 1

sherpa> load_user_model( &myline, "ml" );
sherpa> add_user_pars( ml, ["m","b"] );

Load a user model called "ml" and then add two parameters, "m" and "b". The default settings for the parameter values, units, etc. are used.

Example 2

sherpa> add_user_pars( custom, ["slope"], [30]; parunits=["cm/s"],
parfrozen=[1] );

Add a parameter called "slope" to the model "custom". The initial parameter value is 30, the units are cm/s, and the parameter is frozen.

Bugs

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

Last modified: December 2008



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 © 1998-2004. All rights reserved.