[us-commits] [ehb54/ultrascan3] 26e872: SAXS extrap-to-c0: handle already-normalized I*(q)...

[emre brookes]

  Branch: refs/heads/ehb54-issue-920
  Home:   https://github.com/ehb54/ultrascan3
  Commit: 26e872e06367692095f323149f9f66f2f48ede60
      https://github.com/ehb54/ultrascan3/commit/26e872e06367692095f323149f9f66f2f48ede60
  Author: ehb54 <brookes at uthscsa.edu>
  Date:   2026-07-11 (Sat, 11 Jul 2026)

  Changed paths:
    M us_somo/develop/src/us_hydrodyn_saxs_iqq_extrap_c0.cpp
    M us_somo/somo/doc/manual/somo/somo_saxs_extrap_c0.html

  Log Message:
  -----------
  SAXS extrap-to-c0: handle already-normalized I*(q) inputs

Curves named "*_Istarq_*" are already I*(q) (header units g/mol,
I(0)=MW): their intensity is already concentration-normalized even
though their Conc: header is non-unity. Previously the Zimm fit divided
every curve's intensity by its concentration, double-normalizing these.

Now:
  - Zimm mode uses an I*(q) curve's intensity as-is (no divide by c),
    while still using its real concentration as the regression x-axis.
  - A selection made entirely of I*(q) curves yields an already-
    normalized output, tagged Conc:1 in both modes (Primus no longer
    tags it with the reference concentration in that case).
  - Mixing I*(q) and raw-intensity curves in one extrapolation warns
    (different scales), without blocking.
  - Editor messages and the manual page document the behavior.

Primus mode never divides by c, so its intensity handling was already
correct; only its output concentration tag needed the all-I*(q) case.

Co-Authored-By: Claude Fable 5 <noreply at anthropic.com>



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