[GitHub] [spark] cloud-fan commented on a diff in pull request #36708: [SPARK-37623][SQL] Support ANSI Aggregate Function: regr_intercept

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

cloud-fan commented on code in PR #36708:
URL: https://github.com/apache/spark/pull/36708#discussion_r884912975


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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/linearRegression.scala:
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@@ -291,3 +291,52 @@ case class RegrSlope(left: Expression, right: Expression) extends DeclarativeAgg
       newLeft: Expression, newRight: Expression): RegrSlope =
     copy(left = newLeft, right = newRight)
 }
+
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+  usage = "_FUNC_(y, x) - Returns the intercept of the univariate linear regression line for non-null pairs in a group, where `y` is the dependent variable and `x` is the independent variable.",
+  examples = """
+    Examples:
+      > SELECT _FUNC_(y, x) FROM VALUES (1,1), (2,2), (3,3) AS tab(y, x);
+       0.0
+      > 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
+  """,
+  group = "agg_funcs",
+  since = "3.4.0")
+// scalastyle:on line.size.limit
+case class RegrIntercept(left: Expression, right: Expression) extends DeclarativeAggregate
+  with ImplicitCastInputTypes with BinaryLike[Expression] {
+
+  private val regrSlope = RegrSlope(left, right)

Review Comment:
   It looks tricky to have one more level of indirection, can we create `CovPopulation` and `VariancePop` here?



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