Hello I don't understand meaning of the symbol represented by a capital letter "I" in the formulas below. There is a link to the paper with the formulas.

Screen shot from the paper with the symbol I don't understand.

At the beginning I thought it mean "where c is not equal to the result of classifier T(m)", however in step (d) there is a multiplication symbol before it, so it probably mean that "I" should "return" a value.


2 Answers 2


It's the indicator function! It takes value 1 if the condition inside the brackets is met, 0 otherwise.


To add to stochazesthai correct answer.

In your examples the first usage indicates 1 in the case where the prediction of the mth tree does not equal the actual class. If it not equal then 1 is "returned" and so will affect the error term via the weight.


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