[GitHub] [spark] beliefer commented on a change in pull request #34894: [SPARK-37641][SQL] Support ANSI Aggregate Function: regr_r2

[GitBox <gi...@apache.org>]

beliefer commented on a change in pull request #34894:
URL: https://github.com/apache/spark/pull/34894#discussion_r822350284



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/linearRegression.scala
##########
@@ -105,3 +106,34 @@ case class RegrAvgY(left: Expression, right: Expression)
       newLeft: Expression, newRight: Expression): RegrAvgY =
     this.copy(left = newLeft, right = newRight)
 }
+
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+  usage = "_FUNC_(y, x) - Returns the number of non-null number pairs in a group, where `y` is the dependent variable and `x` is the independent variable.",
+  examples = """
+    Examples:
+      > SELECT _FUNC_(y, x) FROM VALUES (1, 2), (2, 2), (2, 3), (2, 4) AS tab(y, x);
+       0.2727272727272727
+      > SELECT _FUNC_(y, x) FROM VALUES (1, null) AS tab(y, x);
+       NULL
+      > SELECT _FUNC_(y, x) FROM VALUES (null, 1) AS tab(y, x);
+       NULL
+      > SELECT _FUNC_(y, x) FROM VALUES (1, 2), (2, null), (2, 3), (2, 4) AS tab(y, x);
+       0.7500000000000001
+      > SELECT _FUNC_(y, x) FROM VALUES (1, 2), (2, null), (null, 3), (2, 4) AS tab(y, x);
+       1.0
+  """,
+  group = "agg_funcs",
+  since = "3.3.0")
+// scalastyle:on line.size.limit
+case class RegrR2(x: Expression, y: Expression) extends PearsonCorrelation(x, y, true) {
+  override def prettyName: String = "regr_r2"
+  override val evaluateExpression: Expression = {
+    lazy val corr = ck / sqrt(xMk * yMk)

Review comment:
       Got it.




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