Github user sethah commented on a diff in the pull request:
https://github.com/apache/spark/pull/16149#discussion_r91956672
--- Diff:
mllib/src/main/scala/org/apache/spark/ml/regression/GeneralizedLinearRegression.scala
---
@@ -467,10 +469,12 @@ object GeneralizedLinearRegression extends
DefaultParamsReadable[GeneralizedLine
override def variance(mu: Double): Double = mu * (1.0 - mu)
+ private def ylogy(y: Double, mu: Double): Double = {
+ if (y == 0) 0.0 else y * math.log(y / mu)
+ }
+
override def deviance(y: Double, mu: Double, weight: Double): Double =
{
--- End diff --
The utility method is not incorrect, I just think the above is more clear.
That is how I've seen it done in e.g. statsmodels, and I think adding a static
method for this simple logic is a bit superfluous. Isn't the entire point of
the static method to avoid the y=0 case, which would calculate log(0), which is
undefined?
Anyway, if we alternately elect to keep the `ylogy` method, I think a short
doc would be helpful.
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