• Novice users should not "need to know hidden features", e.g. for saving their fits, changing fit methods etc
  • "fit pages" have compute & fit buttons, could also have "save fit" and "report" buttons, even "save model".
  • "save fit" could put up a list of "fit, P(Q), S(Q), unsmeared, etc" to choose which to save. [FISH does this]
  • Propose that all form factor models have both "rescale" and "volfraction" as parameters, where rescale defaults to 1.0 (correct for neutron SANS data in absolute units).
  • We could have two versions of each S(Q), one as now, with radius_effective in S(Q) constrained to the geometric parameters in the form factor, and a second where a radius_effective parameter appears which can be separately adjusted - as most of us scientists would rather use this.

Even better, with a single version of each S(Q), radius_effective could always appear, with a three state selector - fitting, fixed or constrained.

  • Such a three state selector would be useful to turn constraints on & off without having to edit the constraints tab. Note the current constraints were originally envisaged as operating between two "Fit Page" tabs rather than within a single "Fit Page" tab, which as a general feature would have consequences for polydispersity integrations.
  • Constraints within a single "Fit Page" tab become particularly usful if there is a way to rapdily introduce an extra parameter.

e.g. I want a new parameter R_ratio =(radius_core + thick_shell)/radius_core but don't want to write a re-parametrised model to fit, or more likely fix, the value of R_ratio. We may decide that in sasview the only good way to do this is actually to have to write a new model….. (sigh).

  • Introduce a system in the models to flag an issue if too many scale parameters being asked to adjust simultaneously. e.g. "Fit One Of(rescale, volfraction, sld_core.AND.sld_shell.AND.sld_solvent )" This is not completely foolproof as it fails if say sld_shell = sld_solvent. In theory the least squares ought to be able to spot perfect correlations then complain also.


  • When fitting data, the fit should only appear on the plot associated with that fit page ( unlike v4.0 where it also appears on plots where the same data is used in other fit pages.)
  • If say S(Q) or P(Q) has been appended to a fit page plot, then they could auto-update. This may be too complex.
  • Better still add controls to the fit plot to "show rescaled S(Q), show P(Q), show unsmeared" etc as appropriate, with these auto-updating. Would have to remove them if S(Q) is removed from the model.
  • Note a "rescaled S(Q)", multiplied by 10n, can be useful on some types of plot, though frequently on a log(I(Q)) plot it looks rather flat!
  • It would be nice to be able to click on a data point on a graph and get its x,y or x,y,z co-ordinates. May or may not want to keep the current ability to get x,y of any point on the plot by mousing over it.
Last modified 18 months ago Last modified on Oct 29, 2017 10:57:14 AM