Merge pull request #460 from s22s/feature/local_sqrt

Add rf_sqrt square root

Author: vpipkt

core/src/main/scala/org/locationtech/rasterframes/expressions/localops/Exp.scala

@@ -112,3 +112,4 @@ case class ExpM1(child: Expression) extends UnaryLocalRasterOp with CodegenFallb
 object ExpM1{
   def apply(tile: Column): Column = new Column(ExpM1(tile.expr))
 }
+

core/src/main/scala/org/locationtech/rasterframes/expressions/localops/Sqrt.scala

@@ -0,0 +1,50 @@
+/*
+ * This software is licensed under the Apache 2 license, quoted below.
+ *
+ * Copyright 2020 Astraea, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     [http://www.apache.org/licenses/LICENSE-2.0]
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+package org.locationtech.rasterframes.expressions.localops
+
+import geotrellis.raster.Tile
+import org.apache.spark.sql.Column
+import org.apache.spark.sql.catalyst.expressions.codegen.CodegenFallback
+import org.apache.spark.sql.catalyst.expressions.{Expression, ExpressionDescription}
+import org.apache.spark.sql.types.DataType
+import org.locationtech.rasterframes.expressions.{UnaryLocalRasterOp, fpTile}
+
+@ExpressionDescription(
+  usage = "_FUNC_(tile) - Perform cell-wise square root",
+  arguments = """
+  Arguments:
+    * tile - input tile
+  """,
+  examples =
+    """
+    Examples:
+      > SELECT _FUNC_(tile)
+      ... """
+)
+case class Sqrt(child: Expression) extends UnaryLocalRasterOp with CodegenFallback {
+  override val nodeName: String = "rf_sqrt"
+  override protected def op(tile: Tile): Tile = fpTile(tile).localPow(0.5)
+  override def dataType: DataType = child.dataType
+}
+object Sqrt {
+  def apply(tile: Column): Column = new Column(Sqrt(tile.expr))
+}

core/src/main/scala/org/locationtech/rasterframes/expressions/package.scala

@@ -107,6 +107,7 @@ package object expressions {
     registry.registerExpression[Exp10]("rf_exp10")
     registry.registerExpression[Exp2]("rf_exp2")
     registry.registerExpression[ExpM1]("rf_expm1")
+    registry.registerExpression[Sqrt]("rf_sqrt")
     registry.registerExpression[Resample]("rf_resample")
     registry.registerExpression[TileToArrayDouble]("rf_tile_to_array_double")
     registry.registerExpression[TileToArrayInt]("rf_tile_to_array_int")

core/src/main/scala/org/locationtech/rasterframes/functions/LocalFunctions.scala

@@ -299,6 +299,9 @@ trait LocalFunctions {
   /** Exponential of cell values, less one*/
   def rf_expm1(tileCol: Column): Column = ExpM1(tileCol)
 
+  /** Square root of cell values */
+  def rf_sqrt(tileCol: Column): Column = Sqrt(tileCol)
+
   /** Return the incoming tile untouched. */
   def rf_identity(tileCol: Column): Column = Identity(tileCol)
 }

core/src/test/scala/org/locationtech/rasterframes/functions/LocalFunctionsSpec.scala

@@ -298,5 +298,15 @@ class LocalFunctionsSpec extends TestEnvironment with RasterMatchers {
 
     }
 
+    it("should take square root") {
+      checkDocs("rf_sqrt")
+
+      val df = Seq(three).toDF("tile")
+      assertEqual(
+        df.select(rf_sqrt(rf_local_multiply($"tile", $"tile"))).as[ProjectedRasterTile].first(),
+        three
+      )
+    }
+
   }
 }

docs/src/main/paradox/reference.md

@@ -559,6 +559,13 @@ Performs cell-wise logarithm with base 2.
 
 Performs natural logarithm of cell values plus one. Inverse of @ref:[`rf_expm1`](reference.md#rf-expm1).
 
+
+### rf_sqrt
+
+     Tile rf_sqrt(Tile tile)
+     
+Perform cell-wise square root.
+
 ## Tile Statistics
 
 The following functions compute a statistical summary per row of a `tile` column. The statistics are computed across the cells of a single `tile`, within each DataFrame Row.

docs/src/main/paradox/release-notes.md

@@ -28,6 +28,7 @@
     * Add `rf_local_min`, `rf_local_max`, and `rf_local_clip` functions.
     * Add cell value scaling functions `rf_rescale` and `rf_standardize`.
     * Add `rf_where` function, similar in spirit to numpy's `where`, or a cell-wise version of Spark SQL's `when` and `otherwise`.
+* Add `rf_sqrt` function to compute cell-wise square root.
 
 
 ## 0.8.x

pyrasterframes/src/main/python/pyrasterframes/rasterfunctions.py

@@ -773,6 +773,10 @@ def rf_expm1(tile_col: Column_type) -> Column:
     return _apply_column_function('rf_expm1', tile_col)
 
 
+def rf_sqrt(tile_col: Column_type) -> Column:
+    """Performs cell-wise square root"""
+    return _apply_column_function('rf_sqrt', tile_col)
+
 def rf_identity(tile_col: Column_type) -> Column:
     """Pass tile through unchanged"""
     return _apply_column_function('rf_identity', tile_col)

pyrasterframes/src/main/python/tests/RasterFunctionsTests.py

@@ -102,6 +102,7 @@ def test_general(self):
             .withColumn('log', rf_log('tile')) \
             .withColumn('exp', rf_exp('tile')) \
             .withColumn('expm1', rf_expm1('tile')) \
+            .withColumn('sqrt', rf_sqrt('tile')) \
             .withColumn('round', rf_round('tile')) \
             .withColumn('abs', rf_abs('tile'))