Fix guess.rb_decay not to raise an error against bad output #1336
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itoko
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backport stable potential
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Dec 12, 2023
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This looks reasonable to me. @nkanazawa1989 are you okay with merging?
Co-authored-by: Naoki Kanazawa <nkanazawa1989@gmail.com>
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### Summary
Fixed a bug in `guess.rb_decay` where it unintentionally raises an error
if all y values are below the b value (that can happen in experiments on
real devices).
### Details and comments
Changed to return `0` as the initial guess of the decay parameter when
all y values are below the b value, instead of raising an IndexError
like
```
File "/qiskit-experiments/qiskit_experiments/curve_analysis/guess.py", line 406, in rb_decay
return ((y[0] - b) / a) ** (1 / x[0])
IndexError: index 0 is out of bounds for axis 0 with size 0
```
An alternative solution might be explicitly raising a QiskitError. But,
if we want to raise an error for too bad data to fit, I think the fitter
(not rb_decay) should raise an error because it should not be due to the
failure of guessing initial parameter (that is the object of `rb_decay`
function.
---------
Co-authored-by: Naoki Kanazawa <nkanazawa1989@gmail.com>
(cherry picked from commit 0937bb4)
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Summary
Fixed a bug in
guess.rb_decaywhere it unintentionally raises an error if all y values are below the b value (that can happen in experiments on real devices).Details and comments
Changed to return
0as the initial guess of the decay parameter when all y values are below the b value, instead of raising an IndexError likeAn alternative solution might be explicitly raising a QiskitError. But, if we want to raise an error for too bad data to fit, I think the fitter (not rb_decay) should raise an error because it should not be due to the failure of guessing initial parameter (that is the object of
rb_decayfunction.