add DAVERAGE function support

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1901253 13f79535-47bb-0310-9956-ffa450edef68

poi/src/main/java/org/apache/poi/ss/formula/eval/FunctionEval.java

@@ -107,7 +107,7 @@ public final class FunctionEval {
         retval[39] = NumericFunction.MOD;
         retval[40] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DCOUNT);
         retval[41] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DSUM);
-        // 42: DAVERAGE
+        retval[42] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DAVERAGE);
         retval[43] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DMIN);
         retval[44] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DMAX);
         // 45: DSTDEV

poi/src/main/java/org/apache/poi/ss/formula/functions/DAverage.java

@@ -0,0 +1,54 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You 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.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+import org.apache.poi.ss.formula.eval.NumberEval;
+import org.apache.poi.ss.formula.eval.NumericValueEval;
+import org.apache.poi.ss.formula.eval.ValueEval;
+
+import java.math.BigDecimal;
+import java.math.MathContext;
+
+/**
+ * Implementation of the DAverage function:
+ * Gets the average value of a column in an area with given conditions.
+ */
+public final class DAverage implements IDStarAlgorithm {
+    private int count;
+    private double total;
+
+    @Override
+    public boolean processMatch(ValueEval eval) {
+        if (eval instanceof NumericValueEval) {
+            count++;
+            total += ((NumericValueEval)eval).getNumberValue();
+        }
+        return true;
+    }
+
+    @Override
+    public ValueEval getResult() {
+        return count == 0 ? NumberEval.ZERO : new NumberEval(getAverage());
+    }
+
+    private double getAverage() {
+        return BigDecimal.valueOf(total)
+                .divide(BigDecimal.valueOf(count), MathContext.DECIMAL128)
+                .doubleValue();
+    }
+}

poi/src/main/java/org/apache/poi/ss/formula/functions/DStarRunner.java

@@ -60,6 +60,8 @@ public final class DStarRunner implements Function3Arg {
         DSUM(DSum::new),
         /** @see DCount */
         DCOUNT(DCount::new),
+        /** @see DAverage */
+        DAVERAGE(DAverage::new),
         ;
 
         private final Supplier<IDStarAlgorithm> implSupplier;

poi/src/test/java/org/apache/poi/ss/formula/functions/TestDAverage.java

@@ -0,0 +1,62 @@
+
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You 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.
+==================================================================== */
+package org.apache.poi.ss.formula.functions;
+
+import org.apache.poi.hssf.usermodel.HSSFCell;
+import org.apache.poi.hssf.usermodel.HSSFFormulaEvaluator;
+import org.apache.poi.hssf.usermodel.HSSFSheet;
+import org.apache.poi.hssf.usermodel.HSSFWorkbook;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+
+import static org.apache.poi.ss.util.Utils.addRow;
+import static org.apache.poi.ss.util.Utils.assertDouble;
+
+/**
+ * Testcase for function DAVERAGE()
+ */
+public class TestDAverage {
+
+    //https://support.microsoft.com/en-us/office/daverage-function-a6a2d5ac-4b4b-48cd-a1d8-7b37834e5aee
+    @Test
+    void testMicrosoftExample1() throws IOException {
+        try (HSSFWorkbook wb = initWorkbook1()) {
+            HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+            HSSFCell cell = wb.getSheetAt(0).getRow(0).createCell(12);
+            assertDouble(fe, cell, "DAVERAGE(A4:E10, \"Yield\", A1:B2)", 12);
+            assertDouble(fe, cell, "DAVERAGE(A4:E10, 3, A4:E10)", 13);
+        }
+    }
+
+    private HSSFWorkbook initWorkbook1() {
+        HSSFWorkbook wb = new HSSFWorkbook();
+        HSSFSheet sheet = wb.createSheet();
+        addRow(sheet, 0, "Tree", "Height", "Age", "Yield", "Profit", "Height");
+        addRow(sheet, 1, "=Apple", ">10", null, null, null, "<16");
+        addRow(sheet, 2, "=Pear");
+        addRow(sheet, 3, "Tree", "Height", "Age", "Yield", "Profit");
+        addRow(sheet, 4, "Apple", 18, 20, 14, 105);
+        addRow(sheet, 5, "Pear", 12, 12, 10, 96);
+        addRow(sheet, 6, "Cherry", 13, 14, 9, 105);
+        addRow(sheet, 7, "Apple", 14, 15, 10, 75);
+        addRow(sheet, 8, "Pear", 9, 8, 8, 76.8);
+        addRow(sheet, 9, "Apple", 8, 9, 6, 45);
+        return wb;
+    }
+}