[bug-64258] support TDIST function

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1894378 13f79535-47bb-0310-9956-ffa450edef68

4 files changed, 218 insertions, 1 deletions

diff --git a/poi/src/main/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java b/poi/src/main/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
index 703dd3e7a4..927b85d621 100644
--- a/poi/src/main/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
+++ b/poi/src/main/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
@@ -173,6 +173,7 @@ public final class AnalysisToolPak implements UDFFinder {
         r(m, "TBILLEQ", null);
         r(m, "TBILLPRICE", null);
         r(m, "TBILLYIELD", null);
+        //r(m, "TDIST.AR", TDist.instance);
         r(m, "TEXTJOIN", TextJoinFunction.instance);
         r(m, "WEEKNUM", WeekNum.instance);
         r(m, "WORKDAY", WorkdayFunction.instance);
diff --git a/poi/src/main/java/org/apache/poi/ss/formula/eval/FunctionEval.java b/poi/src/main/java/org/apache/poi/ss/formula/eval/FunctionEval.java
index f0fc275844..d8c44c319c 100644
--- a/poi/src/main/java/org/apache/poi/ss/formula/eval/FunctionEval.java
+++ b/poi/src/main/java/org/apache/poi/ss/formula/eval/FunctionEval.java
@@ -281,7 +281,7 @@ public final class FunctionEval {
         retval[298] = NumericFunction.ODD;
         // 299: PERMUT
         retval[300] = NumericFunction.POISSON;
-        // 301: TDIST
+        retval[301] = TDist.instance;
         // 302: WEIBULL
         retval[303] = new Sumxmy2();
         retval[304] = new Sumx2my2();
diff --git a/poi/src/main/java/org/apache/poi/ss/formula/functions/TDist.java b/poi/src/main/java/org/apache/poi/ss/formula/functions/TDist.java
new file mode 100644
index 0000000000..84cea9894a
--- /dev/null
+++ b/poi/src/main/java/org/apache/poi/ss/formula/functions/TDist.java
@@ -0,0 +1,112 @@
+/* ====================================================================
+   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.commons.math3.distribution.TDistribution;
+import org.apache.poi.ss.formula.OperationEvaluationContext;
+import org.apache.poi.ss.formula.eval.*;
+
+/**
+ * Implementation for Excel TDIST() function.
+ * <p>
+ * <b>Syntax</b>:<br> <b>TDIST </b>(<b>X</b>,<b>Deg_freedom</b>,<b>Tails</b>)<br>
+ * <p>
+ * Returns the Percentage Points (probability) for the Student t-distribution where a numeric value (x)
+ * is a calculated value of t for which the Percentage Points are to be computed. The t-distribution is used
+ * in the hypothesis testing of small sample data sets. Use this function in place of a table of critical values
+ * for the t-distribution.
+ *
+ * <ul>
+ *     <li>X     Required. The numeric value at which to evaluate the distribution.</li>
+ *     <li>Deg_freedom     Required. An integer indicating the number of degrees of freedom.</li>
+ *     <li>Tails     Required. Specifies the number of distribution tails to return. If Tails = 1, TDIST returns the
+ *     one-tailed distribution. If Tails = 2, TDIST returns the two-tailed distribution.</li>
+ * </ul>
+ *
+ * <ul>
+ *     <li>If any argument is non-numeric, TDIST returns the #VALUE! error value.</li>
+ *     <li>If Deg_freedom < 1, TDIST returns the #NUM! error value.</li>
+ *     <li>The Deg_freedom and Tails arguments are truncated to integers.
+ *     <li>If Tails is any value other than 1 or 2, TDIST returns the #NUM! error value.</li>
+ *     <li>If x < 0, then TDIST returns the #NUM! error value.</li>
+ * </ul>
+ */
+public final class TDist extends Fixed3ArgFunction implements FreeRefFunction {
+
+    public static final TDist instance = new TDist();
+
+    static double tdistOneTail(double x, int degreesOfFreedom) {
+        TDistribution tdist = new TDistribution(degreesOfFreedom);
+        return 1.0 - tdist.cumulativeProbability(x);
+    }
+
+    static double tdistTwoTails(double x, int degreesOfFreedom) {
+        return 2 * tdistOneTail(x, degreesOfFreedom);
+    }
+
+    @Override
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg1, ValueEval arg2, ValueEval arg3) {
+        try {
+            Double number1 = evaluateValue(arg1, srcRowIndex, srcColumnIndex);
+            if (number1 == null) {
+                return ErrorEval.VALUE_INVALID;
+            } else if (number1 < 0) {
+                return ErrorEval.NUM_ERROR;
+            }
+            Double number2 = evaluateValue(arg2, srcRowIndex, srcColumnIndex);
+            if (number2 == null) {
+                return ErrorEval.VALUE_INVALID;
+            }
+            int degreesOfFreedom = number2.intValue();
+            if (degreesOfFreedom < 1) {
+                return ErrorEval.NUM_ERROR;
+            }
+            Double number3 = evaluateValue(arg3, srcRowIndex, srcColumnIndex);
+            if (number3 == null) {
+                return ErrorEval.VALUE_INVALID;
+            }
+            int tails = number3.intValue();
+            if (!(tails == 1 || tails == 2)) {
+                return ErrorEval.NUM_ERROR;
+            }
+
+            if (tails == 2) {
+                return new NumberEval(tdistTwoTails(number1, degreesOfFreedom));
+            }
+
+            return new NumberEval(tdistOneTail(number1, degreesOfFreedom));
+        } catch (EvaluationException e) {
+            return e.getErrorEval();
+        }
+    }
+
+    @Override
+    public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
+         if (args.length == 3) {
+            return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0], args[1], args[2]);
+        }
+
+        return ErrorEval.VALUE_INVALID;
+    }
+
+    private static Double evaluateValue(ValueEval arg, int srcRowIndex, int srcColumnIndex) throws EvaluationException {
+        ValueEval veText = OperandResolver.getSingleValue(arg, srcRowIndex, srcColumnIndex);
+        String strText1 = OperandResolver.coerceValueToString(veText);
+        return OperandResolver.parseDouble(strText1);
+    }
+}
\ No newline at end of file
diff --git a/poi/src/test/java/org/apache/poi/ss/formula/functions/TestTDist.java b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestTDist.java
new file mode 100644
index 0000000000..4698455b2a
--- /dev/null
+++ b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestTDist.java
@@ -0,0 +1,104 @@
+/* ====================================================================
+   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.apache.poi.ss.formula.OperationEvaluationContext;
+import org.apache.poi.ss.formula.eval.ErrorEval;
+import org.apache.poi.ss.formula.eval.NumberEval;
+import org.apache.poi.ss.formula.eval.StringEval;
+import org.apache.poi.ss.formula.eval.ValueEval;
+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;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Tests for {@link TDist}
+ */
+final class TestTDist {
+
+    private static final OperationEvaluationContext ec = new OperationEvaluationContext(null, null, 0, 0, 0, null);
+
+    @Test
+    void testBasic() {
+        confirmValue("5.968191467", "8", "1", 0.00016754180265310392);
+        confirmValue("5.968191467", "8", "2", 0.00033508360530620784);
+        confirmValue("5.968191467", "8.2", "2.2", 0.00033508360530620784);
+        confirmValue("5.968191467", "8.9", "2.9", 0.00033508360530620784);
+    }
+
+    @Test
+    void testInvalid() {
+        confirmInvalidError("A1","B2","C2");
+        confirmInvalidError("5.968191467","8","C2");
+        confirmInvalidError("5.968191467","B2","2");
+        confirmInvalidError("A1","8","2");
+    }
+
+    @Test
+    void testNumError() {
+        confirmNumError("5.968191467", "8", "0");
+        confirmNumError("-5.968191467", "8", "2");
+    }
+
+    //https://support.microsoft.com/en-us/office/tdist-function-630a7695-4021-4853-9468-4a1f9dcdd192
+    @Test
+    void testMicrosoftExample1() throws IOException {
+        try (HSSFWorkbook wb = new HSSFWorkbook()) {
+            HSSFSheet sheet = wb.createSheet();
+            addRow(sheet, 0, "Data", "Description");
+            addRow(sheet, 1, 1.959999998, "Value at which to evaluate the distribution");
+            addRow(sheet, 2, 60, "Degrees of freedom");
+            HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+            HSSFCell cell = wb.getSheetAt(0).getRow(0).createCell(100);
+            assertDouble(fe, cell, "TDIST(A2,A3,2)", 0.054644930, 0.01);
+            assertDouble(fe, cell, "TDIST(A2,A3,1)", 0.027322465, 0.01);
+        }
+    }
+
+    private static ValueEval invokeValue(String number1, String number2, String number3) {
+        ValueEval[] args = new ValueEval[] { new StringEval(number1), new StringEval(number2), new StringEval(number3)};
+        return TDist.instance.evaluate(args, ec);
+    }
+
+    private static void confirmValue(String number1, String number2, String number3, double expected) {
+        ValueEval result = invokeValue(number1, number2, number3);
+        assertEquals(NumberEval.class, result.getClass());
+        assertEquals(expected, ((NumberEval) result).getNumberValue(), 0.0);
+    }
+
+    private static void confirmInvalidError(String number1, String number2, String number3) {
+        ValueEval result = invokeValue(number1, number2, number3);
+        assertEquals(ErrorEval.class, result.getClass());
+        assertEquals(ErrorEval.VALUE_INVALID, result);
+    }
+
+    private static void confirmNumError(String number1, String number2, String number3) {
+        ValueEval result = invokeValue(number1, number2, number3);
+        assertEquals(ErrorEval.class, result.getClass());
+        assertEquals(ErrorEval.NUM_ERROR, result);
+    }
+
+}