[BUG] Pake preview (and fit) not working #308

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opened 2025-03-13 08:04:35 +00:00 by saeckech · 5 comments
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Current behavior

In order to check D2O coupling parameters, I wanted to (manually) fit a Pake spectrum to partially frozen water data (appended 'data'-data). This worked fine some time ago (appended 'preview_old'-data and image). Today, trying to repeat everything with changed fit/preview parameters (eta=0 instead of 0.1), the preview does not appear and a fit (levenberg-marquard) gives the error message 'residuals not finite at the initial point'. Fitparameters were fixed or (reasonably?) restrained. Nelder-Mead and ODR calculate something upon fitting, but yield only NaN.

Version

2025-02-13

Expected behavior

Concisely, I expected a Pake-shaped something to appear

Steps to reproduce

No response

Log messages

13/03/2025 08:09:52 - ERROR - root : Residuals are not finite in the initial point.
NoneType: None

Anything else?

the python-2 version of the auswerteprogram at Mathilda's computer manages a preview, but the preview looks weird. I'm guessing it has too few x-values.
I tried fits and preview with and without excluding the narrowed line of the spectrum

### Current behavior In order to check D2O coupling parameters, I wanted to (manually) fit a Pake spectrum to partially frozen water data (appended 'data'-data). This worked fine some time ago (appended 'preview_old'-data and image). Today, trying to repeat everything with changed fit/preview parameters (eta=0 instead of 0.1), the preview does not appear and a fit (levenberg-marquard) gives the error message 'residuals not finite at the initial point'. Fitparameters were fixed or (reasonably?) restrained. Nelder-Mead and ODR calculate something upon fitting, but yield only NaN. ### Version 2025-02-13 ### Expected behavior Concisely, I expected a Pake-shaped something to appear ### Steps to reproduce _No response_ ### Log messages ```shell 13/03/2025 08:09:52 - ERROR - root : Residuals are not finite in the initial point. NoneType: None ``` ### Anything else? the python-2 version of the auswerteprogram at Mathilda's computer manages a preview, but the preview looks weird. I'm guessing it has too few x-values. I tried fits and preview with and without excluding the narrowed line of the spectrum
saeckech added the
Kind/Bug
label 2025-03-13 08:04:35 +00:00
dominik was assigned by saeckech 2025-03-13 08:04:35 +00:00
Member

Hm, works for me. Most often a problem of ill-chosen start parameters and bounds. What did you use as initial values?

Hm, works for me. Most often a problem of ill-chosen start parameters and bounds. What did you use as initial values?
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I used the values which worked previously for A, delta, eta, Sigma_B and t_pulse. I also tried different values for A over several orders of magnitude, eta=0.0 and Sigma_B=1,0.1 and tried out both t_pulse=2.5 and t_pulse=2.5e-6.

I used the values which worked previously for A, delta, eta, Sigma_B and t_pulse. I also tried different values for A over several orders of magnitude, eta=0.0 and Sigma_B=1,0.1 and tried out both t_pulse=2.5 and t_pulse=2.5e-6.
Member

I see ze problem: Sigma_B is too small, anything below a couple 100 Hz breaks the calculation.

I see ze problem: Sigma_B is too small, anything below a couple 100 Hz breaks the calculation.
Author
Member

also solves the problem for me :)
is it a pake- / histogram-specific issue, or could it happen for normal functions as well?

also solves the problem for me :) is it a pake- / histogram-specific issue, or could it happen for normal functions as well?
Member

This one is due to Pake weirdness.

This one is due to Pake weirdness.
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Reference: IPKM/nmreval#308
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