xgboost sklearn wrapper value 0for Parameter num_class should be greater equal to 1

python scikit-learn xgboost
LetsPlayYahtzee picture LetsPlayYahtzee · Oct 18, 2016 · Viewed 10.2k times · Source

I am trying to use the XGBClassifier wrapper provided by sklearn for a multiclass problem. My classes are [0, 1, 2], the objective that I use is multi:softmax. When I am trying to fit the classifier I get

xgboost.core.XGBoostError: value 0for Parameter num_class should be greater equal to 1

If I try to set the num_class parameter the I get the error

got an unexpected keyword argument 'num_class'

Sklearn is setting this parameter automatically so I am not supposed to pass that argument. But why do I get the first error?

Answer

Czyzby picture Czyzby · Aug 13, 2018

In my case, the same error was thrown during a regular fit call. The root of the issue was that the objective was manually set to multi:softmax, but there were only 2 classes. Changing it to binary:logistic solved the problem.

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