Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/8079#discussion_r36792673
--- Diff:
mllib/src/main/scala/org/apache/spark/ml/classification/LogisticRegression.scala
---
@@ -43,36 +42,76 @@ import org.apache.spark.storage.StorageLevel
*/
private[classification] trait LogisticRegressionParams extends
ProbabilisticClassifierParams
with HasRegParam with HasElasticNetParam with HasMaxIter with
HasFitIntercept with HasTol
- with HasStandardization {
+ with HasStandardization with HasThreshold {
/**
- * Version of setThresholds() for binary classification, available for
backwards
- * compatibility.
+ * Set threshold in binary classification prediction, in range [0, 1].
*
- * Calling this with threshold p will effectively call
`setThresholds(Array(1-p, p))`.
+ * If the estimated probability of class label 1 is > threshold, then
predict 1, else 0.
+ * A high threshold encourages the model to predict 0 more often;
+ * a low threshold encourages the model to predict 1 more often.
*
- * Default is effectively 0.5.
+ * Note: Calling this with threshold p is equivalent to calling
`setThresholds(Array(1-p, p))`.
+ * If both [[threshold]] and [[thresholds]] are set, then they
must agree in this way,
+ * else an [[IllegalArgumentException]] will be thrown.
+ *
+ * Default is 0.5.
* @group setParam
*/
- def setThreshold(value: Double): this.type = set(thresholds, Array(1.0 -
value, value))
+ def setThreshold(value: Double): this.type
/**
- * Version of [[getThresholds()]] for binary classification, available
for backwards
- * compatibility.
+ * Get threshold for binary classification prediction.
*
- * Param thresholds must have length 2 (or not be specified).
- * This returns {{{1 / (1 + thresholds(0) / thresholds(1))}}}.
+ * @return If [[threshold]] is set, returns that value.
+ * Otherwise, if [[thresholds]] is set with length 2 (i.e.,
binary classification),
+ * this returns the equivalent threshold: {{{1 / (1 +
thresholds(0) / thresholds(1))}}}.
+ * Otherwise, returns [[threshold]] default value.
+ * @group getParam
+ * @throws RuntimeException if [[thresholds]] is set to an array of
length other than 2.
+ */
--- End diff --
Right
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