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I'm currently trying to do supervised learning with three classes (let's say A, B and C). I have a ground-truth which is a bit peculiar, because i have 'membership probabilities/compatibilites' distributed between the three classes for all data.

For example, the ground truth for a data '1' may be '0.80 A, 0.15 B, 0.05 C'. For a data '2', it can be '0.45 A, 0.1 B, 0.45 C' (each score is between 0 and 1 and the sum of the three scores is always equal to 1).

My problem is that i don't find a way to fully exploit these informations:

  • If i do classification, my ground truth is transformed to "1 0 0", and it's pretty annoying because for a data with a very balanced ground-truth, almost half of the information is lost.
  • If i do (multiple-)regression on a 3-dimension vector, i don't take into account the fact that the three results are very correlated (the sum is equal to 1, and the score B cannot be the smallest), as the three prediction will be totally independent.

I have very few data available, so i try to keep the maximum information from them.

I did several researches with the tag 'multi-label' or 'multi-output', but i didn't found anything very relevant.

What's the better way for learning from 'distributed ground-truth' like this ? I'm open to any idea.

Thanks,

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You can use logistic regression. After all the outputs of logistic functions are probablity of data belonging to each class. In a typical problem you have hard assignments, but the logistic regression produces the class probablities which approach the hard assignments. You may need to modify the standard logistic regression algorithm a bit so that you can use probablities instead of hard assignments.

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  • $\begingroup$ Ok, thanks for your response. Do you think i could do the same with naive bayes ? Because it's the classifier which produced the best results so far, with hard assignments (logictic regression did pretty good results aswell). $\endgroup$ – mprl May 4 '17 at 7:59
  • $\begingroup$ I think in theory you can use the soft assignments for training any classifiers. For example if you want to train a naive Bayes classifier when calculating the probabilities instead of counting (for a binomial or multinomial event model) you can add the soft assignments. $\endgroup$ – Hooman May 8 '17 at 14:32
  • $\begingroup$ Do you know if the Naive Bayes algorithm has to be modified to do that ? For example, with logistic regression, it appears that the cost function has to be modified to handle training with non-binary classes. Am i wrong ? $\endgroup$ – mprl May 12 '17 at 15:15

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