+ *
+ * Syntax
+ * FREQUENCY(data_array, bins_array)
+ *
+ * data_array Required. An array of or reference to a set of values for which you want to count frequencies.
+ * If data_array contains no values, FREQUENCY returns an array of zeros.
+ * bins_array Required. An array of or reference to intervals into which you want to group the values in data_array.
+ * If bins_array contains no values, FREQUENCY returns the number of elements in data_array.
+ *
+ * @author Yegor Kozlov
+ */
+public class Frequency extends Fixed2ArgFunction {
+ public static final Function instance = new Frequency();
+
+ private Frequency() {
+ // enforce singleton
+ }
+
+ public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
+ MatrixFunction.MutableValueCollector collector = new MatrixFunction.MutableValueCollector(false, false);
+
+ double[] values;
+ double[] bins;
+ try {
+ values = collector.collectValues(arg0);
+ bins = collector.collectValues(arg1);
+ } catch (EvaluationException e) {
+ return e.getErrorEval();
+ }
+
+ // can bins be not sorted?
+ //bins = Arrays.stream(bins).sorted().distinct().toArray();
+
+ int[] histogram = histogram(values, bins);
+ NumberEval[] result = Arrays.stream(histogram).boxed().map(NumberEval::new).toArray(NumberEval[]::new);
+ return new CacheAreaEval(srcRowIndex, srcColumnIndex,
+ srcRowIndex + result.length - 1, srcColumnIndex, result);
+ }
+
+ static int findBin(double value, double[] bins) {
+ int idx = Arrays.binarySearch(bins, value);
+ return idx >= 0 ? idx + 1 : -idx;
+ }
+
+ static int[] histogram(double[] values, double[] bins) {
+ int[] histogram = new int[bins.length + 1];
+ for (double val : values) {
+ histogram[findBin(val, bins) - 1]++;
+ }
+ return histogram;
+ }
+}
diff --git a/src/testcases/org/apache/poi/ss/formula/functions/TestFrequency.java b/src/testcases/org/apache/poi/ss/formula/functions/TestFrequency.java
new file mode 100644
index 000000000..c441c82ad
--- /dev/null
+++ b/src/testcases/org/apache/poi/ss/formula/functions/TestFrequency.java
@@ -0,0 +1,91 @@
+/* ====================================================================
+ 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.HSSFWorkbook;
+import org.apache.poi.ss.usermodel.*;
+import org.apache.poi.ss.util.CellRangeAddress;
+import org.junit.Test;
+
+import static org.apache.poi.ss.formula.functions.Frequency.histogram;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Testcase for the function FREQUENCY(data, bins)
+ *
+ * @author Yegor Kozlov
+ */
+public class TestFrequency {
+
+ @Test
+ public void testHistogram() {
+ assertArrayEquals(new int[]{3, 2, 2, 0, 1, 1},
+ histogram(
+ new double[]{11, 12, 13, 21, 29, 36, 40, 58, 69},
+ new double[]{20, 30, 40, 50, 60})
+ );
+
+ assertArrayEquals(new int[]{1, 1, 1, 1, 1, 0},
+ histogram(
+ new double[]{20, 30, 40, 50, 60},
+ new double[]{20, 30, 40, 50, 60})
+
+ );
+
+ assertArrayEquals(new int[]{2, 3},
+ histogram(
+ new double[]{20, 30, 40, 50, 60},
+ new double[]{30})
+
+ );
+ }
+
+ @Test
+ public void testEvaluate() {
+ Workbook wb = new HSSFWorkbook();
+ FormulaEvaluator evaluator = wb.getCreationHelper().createFormulaEvaluator();
+
+ int[] data = {1, 1, 2, 3, 4, 4, 5, 7, 8, 9, 9, 11, 3, 5, 8};
+ int[] bins = {3, 6, 9};
+ Sheet sheet = wb.createSheet();
+ Row dataRow = sheet.createRow(0); // A1:O1
+ for (int i = 0; i < data.length; i++) {
+ dataRow.createCell(i).setCellValue(data[i]);
+ }
+ Row binsRow = sheet.createRow(1);
+ for (int i = 0; i < bins.length; i++) { // A2:C2
+ binsRow.createCell(i).setCellValue(bins[i]);
+ }
+ Row fmlaRow = sheet.createRow(2);
+ CellRange arrayFmla = sheet.setArrayFormula("FREQUENCY(A1:O1,A2:C2)", CellRangeAddress.valueOf("A3:A6"));
+ Cell b3 = fmlaRow.createCell(1); // B3
+ b3.setCellFormula("COUNT(FREQUENCY(A1:O1,A2:C2))"); // frequency returns a vertical array of bins+1
+
+ Cell c3 = fmlaRow.createCell(2);
+ c3.setCellFormula("SUM(FREQUENCY(A1:O1,A2:C2))"); // sum of the frequency bins should add up to the number of data values
+
+ assertEquals(5, (int) evaluator.evaluate(arrayFmla.getFlattenedCells()[0]).getNumberValue());
+ assertEquals(4, (int) evaluator.evaluate(arrayFmla.getFlattenedCells()[1]).getNumberValue());
+ assertEquals(5, (int) evaluator.evaluate(arrayFmla.getFlattenedCells()[2]).getNumberValue());
+ assertEquals(1, (int) evaluator.evaluate(arrayFmla.getFlattenedCells()[3]).getNumberValue());
+
+ assertEquals(4, (int) evaluator.evaluate(b3).getNumberValue());
+ assertEquals(15, (int) evaluator.evaluate(c3).getNumberValue());
+
+ }
+}