create_decision_tree(): target is not in list #3
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Ever since this project's initial release, the "attributes" parameter to create_decision_tree() has been initialized (at the only non-recursive callsite) from Data.attribute_names, and Data.attribute_names has filtered out the class attribute name. As such, the comment which this commit changes, is inaccurate: the target attribute is specifically *not* in "attributes". The effect of this was that the algorithm would stop splitting one attribute too soon, and thus every leaf node would always contain a non-trivial probability distribution of classifications (conditional, in some unknown way, on the unsplit attribute), but never a single classification with P=1 even when such classifications were possible.
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Ever since this project's initial release, the "attributes" parameter to create_decision_tree() has been initialized (at the only non-recursive callsite) from Data.attribute_names, and Data.attribute_names has filtered out the class attribute name. As such, the comment which this commit changes, is inaccurate: the target attribute is specifically not in the "attributes" parameter. The effect of this mismatch—in my experience using this package—was that the algorithm would stop splitting one attribute too soon, and thus every leaf node would always contain a non-trivial probability distribution of classifications (conditional, in some unknown way, on the unsplit attribute), but never a single classification with P=1 even when such classifications were possible.
This change amends the incorrect comment, removes the subtraction-by-1 and adds an assertion to verify that subtraction-by-1 is not necessary.