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https://issues.apache.org/jira/browse/SYSTEMML-700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15518637#comment-15518637
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Jeremy commented on SYSTEMML-700:
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Hi Matthias,
The solution I'm currently using in HydraR is to transform the labels from
whatever values they are to 0, 1, 2 ... before hand, and then transform them
back to their original labels after the algorithm runs.
Currently the algorithm doesn't handle class values that don't start at 0 or 1,
and doesn't handle non-contiguous integers, both of which can come up. For
example, the result for class labels 4,5,6 will return 5 sets of coefficients
(correct number should be 2), and class labels -1, 0, 1 returns just one set of
coefficients (correct number should be 2).
Handling frames with strings would be a really great user experience - that
could look like R's coercion internally. Both glmnet and scikit-learn handle
string label arguments, but both apis are weakly typed as well.
> Inflexible category labels for Multinomial Logistic Regression
> --------------------------------------------------------------
>
> Key: SYSTEMML-700
> URL: https://issues.apache.org/jira/browse/SYSTEMML-700
> Project: SystemML
> Issue Type: Bug
> Components: Algorithms
> Reporter: Jeremy
> Priority: Minor
> Original Estimate: 4h
> Remaining Estimate: 4h
>
> The Logistic Regression algorithm requires that category labels be labeled as
> 0 up to the number of classes-1. It should be able to handle any set of
> category labels provided by the user. B_out should have the appropriate size
> regardless of the values of the labels given, and the algorithm should also
> preserve the original labeling for the user.
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