"The FRAC calculation for my data using PmagGUI is problematic" (from Tinghong Zhou at the University of Rochester)

[rminnett]

What command was run:

Using the attached data, Tinghong Zhou asked about the FRAC calculation in PmagGUI.

What happened:

The FRAC value was 0.54 when using a fit from 0 C to the end.

What I expected to happen:

The FRAC value is 1.

Data file(s):

FRAC problem report.zip

Screenshot(s):

PmagPy version:

PmagGUI 4.2.109

[duserzym]

Thanks for raising this issue Rupert. This issue puzzles me for the day today...! I went through Ron's code and dug into the Thellier gui code, couldn't figure out why this happens, couldn't reproduce this error with my own IZZI Thellier data. Finally I reazlied Tinghong's extra thermal demag steps (Z steps) after the NRM measurement but before the first actual "Z" step of the ZI paleointensity experiment messed up the FRAC calculation. After manually removing those steps, everything looks fine: I think the way Thellier gui works now makes sense. We should never mix demag steps with Thellier steps.

What we do need to fix is the description text for specimen_frac tick box in the SPD dialog. The current description for frac is incorrect:

I will keep working on that.