Question Re: Auto classification Error.Impossible to deal non boolean target variable .multiple categories found in Technology Q&A

Auto classification Error.Impossible to deal non boolean target variable .multiple categories found

Former Member — Wed, 11 Jan 2017 04:42:44 GMT

Hi Team

I am trying to classify data into multiple categories using Autoclassification in SAP PA 3.0 .

When I use only two categories the classification is done correctly but when the target variable categories increases the Expert analytics as well as automated analytics gives error.

I am not aware of any limitations on SAP PA to classify data into multiple categories. I believe I am doing somehting wrong . Please help me with this issue.

Re: Auto classification Error.Impossible to deal non boolean target variable .multiple categories found

AbdelhalimDadouche — Wed, 11 Jan 2017 07:23:52 GMT

Hi,

The Auto-Classification (used via Automated or Expert Analytics) is a "binary" classification and not a "multi-class" classification algorithm. Therefore, your target variable can only have 2 possible values.

If you want to address a "multi-class" classification scenario, you potentially have 2 strategies to choose from:

One-vs.-rest (OvR)

The one-vs.-rest (or one-vs.-all) strategy involves training a single classifier per class, with the samples of that class as positive samples and all other samples as negatives. This strategy requires the base classifiers to produce a real-valued confidence score for its decision, rather than just a class label; discrete class labels alone can lead to ambiguities, where multiple classes are predicted for a single sample.

One-vs.-one (OvO)

In the one-vs.-one, one trains K (K − 1) / 2 binary classifiers for a K-way multiclass problem; each receives the samples of a pair of classes from the original training set, and must learn to distinguish these two classes. At prediction time, a voting scheme is applied: all K (K − 1) / 2 classifiers are applied to an unseen sample and the class that got the highest number of “+1” predictions gets predicted by the combined classifier.

You can read the following blog post I wrote a while back:

https://blogs.sap.com/2016/03/09/how-to-handle-multiclass-classification-in-automated-analytics/

Regards

@bdel

Re: Auto classification Error.Impossible to deal non boolean target variable .multiple categories found

Former Member — Thu, 12 Jan 2017 03:57:31 GMT

Thank you so much Abdel for the clarification and detailed explanation.

I agree we would then have to use one of the two methods mentioned above to work around this problem .

I have done multi class based classification using R. ....is there a way we can incorporate this in our SAP PA ...I know we can call R libraries and functions but I would like to see a step by step document which depicts all the processes involved in invoking R via SAP PA.

Thank you again !