Add FunctionXYTransformer

[qtux]

Hi David,

I added a generic transformer which allows one to arbitrarily transform the data (Xt and yt) before or after segmentation using a custom function. Useful examples which come to mind are:

• selecting specific parts of data (e.g. column filter)
• applying filter functions (e.g. bandpass filter EMG data)

I added a safeguard against unintentional sub- or oversampling of the data as this would affect the training data (which is fine) and the test data (which is not fine) . The safeguard can be deactivated to allow for legitimate use cases similar to segmentation or interpolation of the data.

Could you please verify if my reasoning is correct. I would remove the last two commits if it were not.

Cheers, Matthias

[dmbee]

Thanks Matthias. I'll take a closer look on Monday.

[dmbee]

Hi Matthias, what use cases that change the number of samples would you envision beyond interpolation and segmentation?

If you restrict the number of samples in each series to be the same pre and post transform, than would it not make more sense to implement this as a transformer only on X (which would allow filtering, column selection, etc) which seem like very sensible use cases.

Thanks again for this contribution.

• David

[qtux]

Hi David,

I believe you are right, I can think of no other reasons for changing the number of samples in this transformer. I will adapt this and create another pull request for a transformer which operates solely on X with the enforcement of keeping the number of samples unmodified.

Cheers, Matthias

[coveralls]

Pull Request Test Coverage Report for Build 144

• 88 of 88 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 94.289%

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Totals
Change from base Build 137:	0.3%
Covered Lines:	1486
Relevant Lines:	1576

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💛 - Coveralls