ENH: add Function.low_pass_filter method

[kalounis]

Pull request type

• Code changes (bugfix, features)

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally

Current behavior

There were no functions to smooth a Function object.

New behavior

We added a "low_pass_filter" method applying an exponential smoothing to a Function object. This function takes a parameter "alpha" you have to chose to smooth the function.

Breaking change

• No

Additional information

For a given dataset, the larger alpha is, the more closely the filtered function returned will match the function
the smaller alpha is, the smoother the filtered function returned will be (but with a phase shift)

[Gui-FernandesBR]

Overall good Work here! I've made a few suggestions in terms of formatting, the idea is to improve the code readability.

Are you familiar with unit tests? I think it would be nice to have a simple test for the new method.

We can help with that if needed.

Thanks for submitting your first PR, I think this will really improve rocketpy!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1a822a3) 71.16% compared to head (7eb4a73) 71.16%.
Report is 18 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #508      +/-   ##
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- Coverage    71.16%   71.16%   -0.01%     
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  Files           55       55              
  Lines         9273     9279       +6     
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+ Hits          6599     6603       +4     
- Misses        2674     2676       +2     

Flag	Coverage Δ
unittests	71.16% <100.00%> (-0.01%)	⬇️

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[styris00]

Overall good Work here! I've made a few suggestions in terms of formatting, the idea is to improve the code readability.

Are you familiar with unit tests? I think it would be nice to have a simple test for the new method.

We can help with that if needed.

Thanks for submitting your first PR, I think this will really improve rocketpy!

We knew we would have to create some tests at some point but are not familiar with this in python and we do not really know how tests work in RocketPy as well, so we decided to wait to do it with you.

[Gui-FernandesBR]

Overall good Work here! I've made a few suggestions in terms of formatting, the idea is to improve the code readability.
Are you familiar with unit tests? I think it would be nice to have a simple test for the new method.
We can help with that if needed.
Thanks for submitting your first PR, I think this will really improve rocketpy!

We knew we would have to create some tests at some point but are not familiar with this in python and we do not really know how tests work in RocketPy as well, so we decided to wait to do it with you.

That's fine. What you would need to do is basically:

• go to the tests/unit/test_function.py file and
• create a test_low_pass_filter method.
• In this method, make sure you use the low_pass_filter to generate a Function object and guarantee this Function is giving correct results.
• You could assert expected results are within a certain error limit.

My recommendations: first test the type of the return of the method, something like: assert isinstance(res, Function). Sencondly, try to test the function with the extreme values of alpha (0 and 1), and later test with arbitrary values of alpha as well.

We can give more details if you need. @lucasfourier is also currently studying unit tests creation and he could support you as well.

[Gui-FernandesBR]

Great work, this method will be very useful when dealing with real world data.
Thank you again for your contributions!

I've made the two latest commits and rebased the branch, please review it and merge it in your earliest convenience.