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Loss functions
Binary cross entropy
Difference between two probability distributions
$-(y log(\hat{y}) + (1-y) log(1-\hat{y})$
(Negative log, since log in [0,1] is < 0)
Recap entropy:
In bin classification entropy for distribution q(y) with 50:50 classes is: $H(q) = log(2)$
For other distrubition (and in general) with C classes, entropy of distribution is $H(q) = - \sum_{c=1}^C q(y_c) * log(q(y_c))$