Move to nanmean instead of mean

[mrkaiser]

Moving to nanmean allows the use of scorers that return nan without breaking existing functionality

Description

Moved the means to np.nanmean to support scorers that may implement returning

Related issues or pull requests

Link related issues/pull requests here

Pull Request requirements

• Added appropriate unit test functions in the ./mlxtend/*/tests directories
• Ran nosetests ./mlxtend -sv and make sure that all unit tests pass
• Checked the test coverage by running nosetests ./mlxtend --with-coverage
• Checked for style issues by running flake8 ./mlxtend
• Added a note about the modification or contribution to the ./docs/sources/CHANGELOG.md file
• Modify documentation in the appropriate location under mlxtend/docs/sources/ (optional)
• Checked that the Travis-CI build passed at https://travis-ci.org/rasbt/mlxtend

[pep8speaks]

Hello @mrkaiser! Thanks for updating the PR.

• In the file mlxtend/feature_selection/sequential_feature_selector.py, following are the PEP8 issues :

Line 359:61: W291 trailing whitespace

Comment last updated on July 07, 2017 at 14:24 Hours UTC

[mrkaiser]

The build is failing due to an issue with sudo apt-get update

[rasbt]

Thanks for the PR, and sorry about the issues with travis-ci -- I never had any issues with that and it worked up to last weekend. Hm, maybe they changed sth this week. I will look into that and let you know when it's resolved.

[rasbt]

Not sure why this issue occurred. I send in a PR for testing and it worked fine. Maybe, it was a temporary issue with the "trusty" environments on their side -- they changed something last week according to their blog. In any case, I removed the trusty flag (I think it was needed back then for the tensorflow code), and it should work fine now. Could you try again? (maybe with a tiny edit like a whitespace or sth like that and change it back).

PS: The PR looks great so far, thanks!

[coveralls]

Coverage increased (+0.1%) to 89.218% when pulling cea6299 on mrkaiser:nanmean into a457882 on rasbt:master.

[mrkaiser]

@rasbt I have updated the builds and all checks are passing

[rasbt]

That's awesome, thanks for the PR!