Gaussian guess - guess negative Gaussian if peak 'looks' negative.

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If average([y value at minimum x], [y value at maximum x]) > (min(y) + max(y))/2, guess a negative Gaussian instead of a positive one.

For a Guassian with tails higher than midpoint of y-values, negative Gaussian is guessed
For a Gaussian with tails lower than midpoint of y-values, positive Gaussian is guessed

Relevant code is here: https://github.com/ISISComputingGroup/ibex_bluesky_core/blob/5de624a00d4236d36f0d2e606afea9c22892e842/src/ibex_bluesky_core/fitting.py#L159
When guessing a negative Gaussian:
- We still want to guess the centre & width using centre-of-mass - but this will now be centre-of-mass of inverted data. The easiest way to do this will be to guess the centre & width using cen, width = _guess_cen_and_width(x, -y).
- Background guess is max(y)
- Amplitude guess is min(y) - max(y)

Research direction: Implement the logic in the fitting.py file to check if the average of y at endpoints is greater than the midpoint of min and max y, then guess a negative Gaussian by inverting the data for centre/width estimation and setting background to max(y) and amplitude to min(y) max(y).
Tech stack: python
Domain: backend
Issue type: Feature
Difficulty: 2
Estimated time: 1-3 hours
Activity status: Active
Clarity: Clear
Prerequisites: PythonBasic understanding of Gaussian fitting
Newbie friendliness: 70