You are viewing a plain text version of this content. The canonical link for it is here.
Posted to commits@commons.apache.org by er...@apache.org on 2011/02/01 13:01:04 UTC
svn commit: r1066018 - in /commons/proper/math/trunk/src:
main/java/org/apache/commons/math/analysis/function/StepFunction.java
test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java
Author: erans
Date: Tue Feb 1 12:01:03 2011
New Revision: 1066018
URL: http://svn.apache.org/viewvc?rev=1066018&view=rev
Log:
MATH-503
Step function.
Added:
commons/proper/math/trunk/src/main/java/org/apache/commons/math/analysis/function/StepFunction.java (with props)
commons/proper/math/trunk/src/test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java (with props)
Added: commons/proper/math/trunk/src/main/java/org/apache/commons/math/analysis/function/StepFunction.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math/analysis/function/StepFunction.java?rev=1066018&view=auto
==============================================================================
--- commons/proper/math/trunk/src/main/java/org/apache/commons/math/analysis/function/StepFunction.java (added)
+++ commons/proper/math/trunk/src/main/java/org/apache/commons/math/analysis/function/StepFunction.java Tue Feb 1 12:01:03 2011
@@ -0,0 +1,89 @@
+/*
+ * 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.commons.math.analysis.function;
+
+import java.util.Arrays;
+import org.apache.commons.math.analysis.UnivariateRealFunction;
+import org.apache.commons.math.exception.DimensionMismatchException;
+import org.apache.commons.math.exception.NullArgumentException;
+import org.apache.commons.math.exception.NoDataException;
+import org.apache.commons.math.util.MathUtils;
+
+/**
+ * <a href="http://en.wikipedia.org/wiki/Step_function">
+ * Step function</a>.
+ *
+ * @version $Revision$ $Date$
+ * @since 3.0
+ */
+public class StepFunction implements UnivariateRealFunction {
+ /** Abscissae. */
+ private final double[] abscissa;
+ /** Ordinates. */
+ private final double[] ordinate;
+
+ /**
+ * Builds a step function from a list of abscissae and the corresponding
+ * ordinates.
+ *
+ * @param x Abscissae.
+ * @param y Ordinates.
+ * @throws org.apache.commons.math.exception.NonMonotonousSequenceException
+ * if the {@code x} array is not sorted in strictly increasing order.
+ * @throws NullArgumentException if {@code x} or {@code y} are {@code null}.
+ * @throws NoDataException if {@code x} or {@code y} are zero-length.
+ */
+ public StepFunction(double[] x,
+ double[] y) {
+ if (x == null ||
+ y == null) {
+ throw new NullArgumentException();
+ }
+ if (x.length == 0 ||
+ y.length == 0) {
+ throw new NoDataException();
+ }
+ if (y.length != x.length) {
+ throw new DimensionMismatchException(y.length, x.length);
+ }
+ MathUtils.checkOrder(x);
+
+ abscissa = MathUtils.copyOf(x);
+ ordinate = MathUtils.copyOf(y);
+ }
+
+ /** {@inheritDoc} */
+ public double value(double x) {
+ int index = Arrays.binarySearch(abscissa, x);
+ double fx = 0;
+
+ if (index < -1) {
+ // "x" is between "abscissa[-index-2]" and "abscissa[-index-1]".
+ fx = ordinate[-index-2];
+ } else if (index >= 0) {
+ // "x" is exactly "abscissa[index]".
+ fx = ordinate[index];
+ } else {
+ // Otherwise, "x" is smaller than the first value in "abscissa"
+ // (hence the returned value should be "ordinate[0]").
+ fx = ordinate[0];
+ }
+
+ return fx;
+ }
+}
Propchange: commons/proper/math/trunk/src/main/java/org/apache/commons/math/analysis/function/StepFunction.java
------------------------------------------------------------------------------
svn:eol-style = native
Added: commons/proper/math/trunk/src/test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java?rev=1066018&view=auto
==============================================================================
--- commons/proper/math/trunk/src/test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java (added)
+++ commons/proper/math/trunk/src/test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java Tue Feb 1 12:01:03 2011
@@ -0,0 +1,95 @@
+/*
+ * 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.commons.math.analysis.function;
+
+import org.apache.commons.math.analysis.UnivariateRealFunction;
+import org.apache.commons.math.exception.DimensionMismatchException;
+import org.apache.commons.math.exception.NonMonotonousSequenceException;
+import org.apache.commons.math.exception.NullArgumentException;
+import org.apache.commons.math.exception.NoDataException;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Test for class {@link StepFunction}.
+ */
+public class StepFunctionTest {
+ private final double EPS = Math.ulp(1d);
+
+ @Test
+ public void testPreconditions() {
+ try {
+ final UnivariateRealFunction f = new StepFunction(null,
+ new double[] {0, -1, -2});
+ } catch (NullArgumentException e) {
+ // Expected.
+ }
+ try {
+ final UnivariateRealFunction f = new StepFunction(new double[] {0, 1},
+ null);
+ } catch (NullArgumentException e) {
+ // Expected.
+ }
+
+ try {
+ final UnivariateRealFunction f = new StepFunction(new double[] {0},
+ new double[] {});
+ } catch (NoDataException e) {
+ // Expected.
+ }
+
+ try {
+ final UnivariateRealFunction f = new StepFunction(new double[] {},
+ new double[] {0});
+ } catch (NoDataException e) {
+ // Expected.
+ }
+
+ try {
+ final UnivariateRealFunction f = new StepFunction(new double[] {0, 1},
+ new double[] {0, -1, -2});
+ } catch (DimensionMismatchException e) {
+ // Expected.
+ }
+
+ try {
+ final UnivariateRealFunction f = new StepFunction(new double[] {1, 0, 1},
+ new double[] {0, -1, -2});
+ } catch (NonMonotonousSequenceException e) {
+ // Expected.
+ }
+ }
+
+ @Test
+ public void testSomeValues() {
+ final double[] x = { -2, -0.5, 0, 1.9, 7.4, 21.3 };
+ final double[] y = { 4, -1, -5.5, 0.4, 5.8, 51.2 };
+
+ final UnivariateRealFunction f = new StepFunction(x, y);
+
+ Assert.assertEquals(4, f.value(Double.NEGATIVE_INFINITY), EPS);
+ Assert.assertEquals(4, f.value(-10), EPS);
+ Assert.assertEquals(-1, f.value(-0.4), EPS);
+ Assert.assertEquals(-5.5, f.value(0), EPS);
+ Assert.assertEquals(0.4, f.value(2), EPS);
+ Assert.assertEquals(5.8, f.value(10), EPS);
+ Assert.assertEquals(51.2, f.value(30), EPS);
+ Assert.assertEquals(51.2, f.value(Double.POSITIVE_INFINITY), EPS);
+ }
+}
Propchange: commons/proper/math/trunk/src/test/java/org/apache/commons/math/analysis/function/StepFunctionTest.java
------------------------------------------------------------------------------
svn:eol-style = native