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…plementForecastFunction Implement forecast function
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| @@ -0,0 +1,150 @@ | ||
| using System; | ||
| using NPOI.SS.Formula.Eval; | ||
|
|
||
| namespace NPOI.SS.Formula.Functions | ||
| { | ||
| /// <summary> | ||
| /// The Forecast class is a representation of the Excel FORECAST function. | ||
| /// This function predicts a future value along a linear trend line based on existing historical data. | ||
| /// The class inherits from the Fixed3ArgFunction class and overrides the Evaluate method. | ||
| /// The Evaluate method takes three arguments: the x-value for which we want to forecast a y-value, | ||
| /// and two arrays of x-values and y-values representing historical data. | ||
| /// The method calculates the slope and intercept of the line of best fit for the historical data | ||
| /// and uses these to calculate the forecast y-value. | ||
| /// The class also includes methods for converting ValueEval objects to numeric arrays and for creating ValueVectors. | ||
| /// </summary> | ||
| public class Forecast : Fixed3ArgFunction | ||
| { | ||
| public override ValueEval Evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1, | ||
| ValueEval arg2) | ||
| { | ||
| try | ||
| { | ||
| if(arg0 is ErrorEval arg0Error) | ||
| { | ||
| return arg0Error; | ||
| } | ||
|
|
||
| if(arg1 is ErrorEval arg1Error) | ||
| { | ||
| return arg1Error; | ||
| } | ||
|
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| if(arg2 is ErrorEval arg2Error) | ||
| { | ||
| return arg2Error; | ||
| } | ||
|
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| double x = NumericFunction.SingleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex); | ||
| double[] yValues = GetNumericArray(arg1); | ||
| double[] xValues = GetNumericArray(arg2); | ||
|
|
||
| if(yValues.Length != xValues.Length) | ||
| { | ||
| return ErrorEval.NA; | ||
| } | ||
|
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| double xSum = 0, ySum = 0, xySum = 0, xSquareSum = 0; | ||
| int n = xValues.Length; | ||
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| for(int i = 0; i < n; i++) | ||
| { | ||
| xSum += xValues[i]; | ||
| ySum += yValues[i]; | ||
| xySum += xValues[i] * yValues[i]; | ||
| xSquareSum += Math.Pow(xValues[i], 2); | ||
| } | ||
|
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| double slope = (n * xySum - xSum * ySum) / (n * xSquareSum - Math.Pow(xSum, 2)); | ||
| double intercept = (ySum - slope * xSum) / n; | ||
|
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| double forecastY = slope * x + intercept; | ||
|
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| return new NumberEval(forecastY); | ||
| } | ||
| catch(EvaluationException e) | ||
| { | ||
| return e.GetErrorEval(); | ||
| } | ||
| } | ||
|
|
||
| private static double[] GetNumericArray(ValueEval arg) | ||
| { | ||
| ValueVector vv = CreateValueVector(arg); | ||
| double[] result = new double[vv.Size]; | ||
| for(int i = 0; i < vv.Size; i++) | ||
| { | ||
| ValueEval v = vv.GetItem(i); | ||
| if(v is ErrorEval errorEval) | ||
| { | ||
| throw new EvaluationException(errorEval); | ||
| } | ||
|
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| if(v is NumberEval numberEval) | ||
| { | ||
| result[i] = numberEval.NumberValue; | ||
| } | ||
| } | ||
|
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| return result; | ||
| } | ||
|
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| private static ValueVector CreateValueVector(ValueEval arg) | ||
| { | ||
| return arg switch { | ||
| ErrorEval eval => throw new EvaluationException(eval), | ||
| TwoDEval dEval => new AreaValueArray(dEval), | ||
| RefEval refEval => new RefValueArray(refEval), | ||
| _ => new SingleCellValueArray(arg) | ||
| }; | ||
| } | ||
|
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| private abstract class ValueArray(int size) : ValueVector | ||
| { | ||
| public ValueEval GetItem(int index) | ||
| { | ||
| if(index < 0 || index > size) | ||
| { | ||
| throw new ArgumentException($"Specified index {index} is outside range (0..{(size - 1)})"); | ||
| } | ||
|
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| return GetItemInternal(index); | ||
| } | ||
|
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| protected abstract ValueEval GetItemInternal(int index); | ||
|
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| public int Size => size; | ||
| } | ||
|
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| private class SingleCellValueArray(ValueEval value) : ValueArray(1) | ||
| { | ||
| protected override ValueEval GetItemInternal(int index) | ||
| { | ||
| return value; | ||
| } | ||
| } | ||
|
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| private class RefValueArray(RefEval ref1) : ValueArray(ref1.NumberOfSheets) | ||
| { | ||
| private readonly int _width = ref1.NumberOfSheets; | ||
|
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| protected override ValueEval GetItemInternal(int index) | ||
| { | ||
| int sIx = (index % _width) + ref1.FirstSheetIndex; | ||
| return ref1.GetInnerValueEval(sIx); | ||
| } | ||
| } | ||
|
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| private class AreaValueArray(TwoDEval ae) : ValueArray(ae.Width * ae.Height) | ||
| { | ||
| private readonly int _width = ae.Width; | ||
|
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| protected override ValueEval GetItemInternal(int index) | ||
| { | ||
| int rowIx = index / _width; | ||
| int colIx = index % _width; | ||
| return ae.GetValue(rowIx, colIx); | ||
| } | ||
| } | ||
| } | ||
| } |
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| /* | ||
| * ==================================================================== | ||
| * 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. | ||
| * ==================================================================== | ||
| */ | ||
|
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||
| namespace TestCases.SS.Formula.Functions | ||
| { | ||
| using NUnit.Framework; | ||
| using System; | ||
| using HSSF; | ||
| using NPOI.SS.Formula.Eval; | ||
| using NPOI.HSSF.UserModel; | ||
| using NPOI.SS.UserModel; | ||
| using NPOI.SS.Formula.Functions; | ||
|
|
||
| /** | ||
| * Test for Excel function FORECAST() | ||
| * | ||
| * @author Ken Smith | ||
| */ | ||
| [TestFixture] | ||
| public class TestForecast | ||
| { | ||
| private static readonly Function FORECAST = new Forecast(); | ||
|
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| /// <summary> | ||
| /// This test is replicated in the "TestBasic" tab of the "Forecast.xls" file. | ||
| /// </summary> | ||
| [Test] | ||
| public void TestBasic() | ||
| { | ||
| ValueEval x = new NumberEval(100); | ||
| ValueEval[] yValues = [ | ||
| new NumberEval(1), | ||
| new NumberEval(2), | ||
| new NumberEval(3), | ||
| new NumberEval(4), | ||
| new NumberEval(5), | ||
| new NumberEval(6) | ||
| ]; | ||
|
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| ValueEval[] xValues = [ | ||
| new NumberEval(2), | ||
| new NumberEval(4), | ||
| new NumberEval(6), | ||
| new NumberEval(8), | ||
| new NumberEval(10), | ||
| new NumberEval(12) | ||
| ]; | ||
| Confirm(x, CreateAreaEval(yValues), CreateAreaEval(xValues), 50.0); | ||
| // Excel 365 build 2402 gives 50.0 | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// This test is replicated in the "TestLargeNumbers" tab of the "Forecast.xls" file. | ||
| /// </summary> | ||
| [Test] | ||
| public void TestLargeNumbers() | ||
| { | ||
| double exp = Math.Pow(10, 7.5); | ||
| ValueEval x = new NumberEval(100); | ||
| ValueEval[] yValues = [ | ||
| new NumberEval(3 + exp), | ||
| new NumberEval(4 + exp), | ||
| new NumberEval(2 + exp), | ||
| new NumberEval(5 + exp), | ||
| new NumberEval(4 + exp), | ||
| new NumberEval(7 + exp) | ||
| ]; | ||
|
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| ValueEval[] xValues = [ | ||
| new NumberEval(1), | ||
| new NumberEval(2), | ||
| new NumberEval(3), | ||
| new NumberEval(4), | ||
| new NumberEval(5), | ||
| new NumberEval(6) | ||
| ]; | ||
| Confirm(x, CreateAreaEval(yValues), CreateAreaEval(xValues), 31622844.1826363); | ||
| // Excel 365 build 2402 gives 31622844.1826363 | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// This test is replicated in the "TestLargeArrays" tab of the "Forecast.xls" file. | ||
| /// </summary> | ||
| [Test] | ||
| public void TestLargeArrays() | ||
| { | ||
| ValueEval x = new NumberEval(100); | ||
| ValueEval[] yValues = CreateMockNumberArray(100, 3); // [2,2,0,1,2,0,...,0,1] | ||
| yValues[0] = new NumberEval(2.0); // Changes first element to 2 | ||
| ValueEval[] xValues = CreateMockNumberArray(100, 101); // [1,2,3,4,...,99,100] | ||
|
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| Confirm(x, CreateAreaEval(yValues), CreateAreaEval(xValues), 0.960990099); | ||
| // Excel 365 build 2402 gives 0.960990099 | ||
| } | ||
|
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| [Test] | ||
| public void TestErrors() | ||
| { | ||
| NumberEval x = new(100); | ||
|
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| ValueEval areaEval1 = CreateAreaEval([new NumberEval(2)]); | ||
| ValueEval areaEval2 = CreateAreaEval([new NumberEval(2), new NumberEval(2)]); // different size | ||
|
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| ValueEval areaEvalWithNullError = CreateAreaEval([new NumberEval(2), ErrorEval.NULL_INTERSECTION]); | ||
| ValueEval areaEvalWithRefError = CreateAreaEval([ErrorEval.REF_INVALID, new NumberEval(2)]); | ||
|
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| // if either arg is an error, that error propagates | ||
| ConfirmError(x, ErrorEval.REF_INVALID, ErrorEval.NAME_INVALID, ErrorEval.REF_INVALID); | ||
| ConfirmError(x, areaEvalWithRefError, ErrorEval.NAME_INVALID, ErrorEval.NAME_INVALID); | ||
| ConfirmError(x, ErrorEval.NAME_INVALID, areaEvalWithRefError, ErrorEval.NAME_INVALID); | ||
|
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| // array sizes must match | ||
| ConfirmError(x, areaEval1, areaEval2, ErrorEval.NA); | ||
|
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| // any error in an array item propagates up | ||
| ConfirmError(x, areaEvalWithRefError, areaEvalWithRefError, ErrorEval.REF_INVALID); | ||
|
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| // search for errors array by array, not pair by pair | ||
| ConfirmError(x, areaEvalWithRefError, areaEvalWithNullError, ErrorEval.REF_INVALID); | ||
| ConfirmError(x, areaEvalWithNullError, areaEvalWithRefError, ErrorEval.NULL_INTERSECTION); | ||
| } | ||
|
|
||
| /** | ||
| * Example from | ||
| * https://support.microsoft.com/en-us/office/forecast-and-forecast-linear-functions-50ca49c9-7b40-4892-94e4-7ad38bbeda99 | ||
| */ | ||
| [Test] | ||
| public void TestFromFile() | ||
| { | ||
| IWorkbook wb = HSSFTestDataSamples.OpenSampleWorkbook("Forecast.xls"); | ||
| HSSFFormulaEvaluator fe = new(wb); | ||
|
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| ISheet example1 = wb.GetSheet("TestFromFile"); | ||
| ICell a8 = example1.GetRow(7).GetCell(0); | ||
| Assert.AreEqual("FORECAST(30,A2:A6,B2:B6)", a8.CellFormula); | ||
| fe.Evaluate(a8); | ||
| Assert.AreEqual(10.60725309, a8.NumericCellValue, 0.00000001); | ||
| } | ||
|
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| private static ValueEval Invoke(ValueEval x, ValueEval yArray, ValueEval xArray) | ||
| { | ||
| ValueEval[] args = [x, yArray, xArray]; | ||
| return FORECAST.Evaluate(args, -1, (short) -1); | ||
| } | ||
|
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| private static void Confirm(ValueEval x, ValueEval yArray, ValueEval xArray, double expected) | ||
| { | ||
| ValueEval result = Invoke(x, yArray, xArray); | ||
| Assert.AreEqual(typeof(NumberEval), result.GetType()); | ||
| Assert.AreEqual(expected, ((NumberEval) result).NumberValue, expected * .000000001); | ||
| } | ||
|
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| private static void ConfirmError(ValueEval x, ValueEval yArray, ValueEval xArray, ErrorEval expectedError) | ||
| { | ||
| ValueEval result = Invoke(x, yArray, xArray); | ||
| Assert.AreEqual(typeof(ErrorEval), result.GetType()); | ||
| Assert.AreEqual(expectedError, (ErrorEval) result); | ||
| } | ||
|
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| private static ValueEval[] CreateMockNumberArray(int size, double value) | ||
| { | ||
| ValueEval[] result = new ValueEval[size]; | ||
| for(int i = 0; i < result.Length; i++) | ||
| { | ||
| result[i] = new NumberEval((i + 1) % value); | ||
| } | ||
|
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| return result; | ||
| } | ||
|
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| private static ValueEval CreateAreaEval(ValueEval[] values) | ||
| { | ||
| string refStr = "A1:A" + values.Length; | ||
| return EvalFactory.CreateAreaEval(refStr, values); | ||
| } | ||
| } | ||
| } |
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