Expose monotonic trend analysis to summary table.

[chunqishi]

Hi, Guillermo.

Thanks a lot for such great package optbinning.
I used it to variable analysis a lot.
One thing is very cool, this lib has great monotonic analysis.

1. This monotonic trend results are useful.
   please check paper: https://ojs.aaai.org/index.php/AAAI/article/view/7055

2. This monotonic analysis can used in boost trees by setting monotonic constraints
   see: https://xgboost.readthedocs.io/en/stable/tutorials/monotonic.html
   see: http://scikit-learn.org/stable/auto_examples/ensemble/plot_monotonic_constraints.html
   see: https://catboost.ai/en/docs/references/training-parameters/common#monotone_constraints

Thus: I modified your develop code by 2 parts.

1. Export the monotonic trend result to binning process summary dataframe.
   

2. Add ranking correlation analysis for continuous binning process to double check monotonic trend output.
   

That's all.

Thank you again.

[guillermo-navas-palencia]

Thanks for your contribution. I like the idea of showing the monotonic trend in the summary. Regarding the monotonic score using the Kendall tau or Spearman rho correlation, I think we can choose just one and rename it simply as correlation.

[chunqishi]

Hi, Guillermo.

Done :- )

[guillermo-navas-palencia]

It looks good! Only a minor change and pass flake8.

[chunqishi]

pull failed?

[guillermo-navas-palencia]

Yes, there are two types of problems:

• print issue when passing None: https://github.com/guillermo-navas-palencia/optbinning/actions/runs/7564258764/job/20778765191?pr=297#step:7:153
• For Python 3.9 and 3.10 tests will not pass due to changes in default solvers of the latest versions of cvxpy/ortools.

I would only focus on the first one. I will deal with the second type before merging to master.

[bmreiniger]

@chunqishi I think this would be a nice addition, can you resolve the first issue above? If needed perhaps we could help, but the logs of the last run have expired; maybe just push a merge from master to kick off a new check?