<RuntimeWarning: invalid value encountered in sqrt>

[Huii]

Thank you very much for this create library, first of all!

The following code in the "distance" function in features.py:

    diff_sig = np.diff(signal)
    return np.sum([np.sqrt(1 + diff_sig ** 2)])

should be changed to:

    diff_sig = np.diff(signal)
    diff_sigFloat = diff_sig.astype(float)
    return np.sum([np.sqrt(1 + diff_sigFloat ** 2)])

The reason for that is that otherwise an integer overflow might occur for larger numbers, which results in negative numbers, which, in turn, results in an "invalid value" error.

[lmfernandes96]

Hi Hui!

Thank you for your interest in TSFEL.

We have followed your suggestion and fixed the bug in the Pull Request #55.
Thank you for contributing to the library, if you find more problems feel free to contact us!