Github user dbtsai commented on a diff in the pull request:
https://github.com/apache/spark/pull/14834#discussion_r78101327
--- Diff:
mllib/src/main/scala/org/apache/spark/ml/classification/LogisticRegression.scala
---
@@ -311,8 +348,25 @@ class LogisticRegression @Since("1.2.0") (
val histogram = labelSummarizer.histogram
val numInvalid = labelSummarizer.countInvalid
- val numClasses = histogram.length
val numFeatures = summarizer.mean.size
+ val numFeaturesPlusIntercept = if (getFitIntercept) numFeatures + 1
else numFeatures
+
+ val numClasses =
MetadataUtils.getNumClasses(dataset.schema($(labelCol))) match {
+ case Some(n: Int) =>
+ require(n >= histogram.length, s"Specified number of classes $n
was " +
+ s"less than the number of unique labels ${histogram.length}.")
+ n
+ case None => histogram.length
+ }
+ val isBinaryClassification = numClasses == 1 || numClasses == 2
+ val isMultinomial = ($(family) == "auto" && !isBinaryClassification) ||
+ ($(family) == "multinomial")
+ val numCoefficientSets = if (isMultinomial) numClasses else 1
+
--- End diff --
maybe it's easier to read
```scala
val (isBinomial, isMultinomial) = {
$(family) match {
case "binomial" =>
require(numClasses == 1 || numClasses == 2, s"Binomial family only
supports 1 or 2 " +
+ s"outcome classes but found $numClasses.")
(true, false)
case "multinomial" =>
(false, true)
case "auto": => ....
case _: throw new IllegalArgExpcetion("Unsupported family")
}
}
```
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