Changeset b7ce5ad in sasview
 Timestamp:
 Mar 28, 2019 12:11:47 PM (6 months ago)
 Branches:
 master, magnetic_scatt
 Children:
 a48831a8
 Parents:
 e40390ee
 File:

 1 edited
Legend:
 Unmodified
 Added
 Removed

src/sas/sasgui/perspectives/fitting/media/fitting_help.rst
r9258c43c rb7ce5ad 338 338 These optimisers form the *Bumps* package written by P Kienzle. For more information 339 339 on each optimiser, see the :ref:`Fitting_Documentation`. 340 341 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ 342 343 Fitting Integer Parameters 344  345 346 Most of the parameters in SasView models will naturally take floating point (decimal) 347 values, but there are some parameters which can only have integer values. Examples 348 include, but are not limited to, the number of shells in a multilayer vesicle, the 349 number of beads in a pearl necklace, the number of arms of a star polymer, and so on. 350 Wherever possible/recognised, the integer nature of a parameter is specified in the 351 respective model documentation and/or parameter table, so read the documentation 352 carefully! 353 354 Integer parameters must be fitted with care. 355 356 Start with your best possible guess for the value of the parameter. And using 357 *a priori* knowledge, fix as many of the other parameters as possible. 358 359 The SasView optimizers treat integer parameters internally as floating point 360 numbers, but the values presented to the user are truncated or rounded, as 361 appropriate. 362 363 In most instances integer parameters will probably be greater than zero. A good 364 policy in such cases is to use a constraint to enforce this. 365 366 Because an integer parameter should, by definition, only move in integer steps, 367 problems may be encountered if the optimizer step size is too small. Similarly, 368 be **very careful** about applying polydispersity to integer parameters. 369 370 The LevenbergMarquardt and QuasiNewton BFGS (and other derivativebased) 371 optimizers are probably best avoided for fitting models with integer parameters. 340 372 341 373 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
Note: See TracChangeset
for help on using the changeset viewer.