From 63d00ba803b5257335daf15bd934c53ba0560f89 Mon Sep 17 00:00:00 2001
From: Luc Maisonobe <luc@apache.org>
Date: Sat, 18 Aug 2012 18:09:45 +0000
Subject: [PATCH] Polynomials now implement the new UnivariateDifferentiable
 interface.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1374630 13f79535-47bb-0310-9956-ffa450edef68
---
 .../polynomials/PolynomialFunction.java       | 25 +++++++++++++++++-
 .../polynomials/PolynomialSplineFunction.java | 26 ++++++++++++++++++-
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialFunction.java b/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialFunction.java
index 3089bacaa..0894546cc 100644
--- a/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialFunction.java
+++ b/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialFunction.java
@@ -25,6 +25,8 @@ import org.apache.commons.math3.exception.NullArgumentException;
 import org.apache.commons.math3.analysis.DifferentiableUnivariateFunction;
 import org.apache.commons.math3.analysis.UnivariateFunction;
 import org.apache.commons.math3.analysis.ParametricUnivariateFunction;
+import org.apache.commons.math3.analysis.differentiation.DerivativeStructure;
+import org.apache.commons.math3.analysis.differentiation.UnivariateDifferentiable;
 import org.apache.commons.math3.util.FastMath;
 import org.apache.commons.math3.util.MathUtils;
 
@@ -36,7 +38,7 @@ import org.apache.commons.math3.util.MathUtils;
  *
  * @version $Id$
  */
-public class PolynomialFunction implements DifferentiableUnivariateFunction, Serializable {
+public class PolynomialFunction implements UnivariateDifferentiable, DifferentiableUnivariateFunction, Serializable {
     /**
      * Serialization identifier
      */
@@ -137,6 +139,27 @@ public class PolynomialFunction implements DifferentiableUnivariateFunction, Ser
         return result;
     }
 
+
+    /** {@inheritDoc}
+     * @since 3.1
+     * @throws NoDataException if {@code coefficients} is empty.
+     * @throws NullArgumentException if {@code coefficients} is {@code null}.
+     */
+    public DerivativeStructure value(final DerivativeStructure t)
+        throws NullArgumentException, NoDataException {
+        MathUtils.checkNotNull(coefficients);
+        int n = coefficients.length;
+        if (n == 0) {
+            throw new NoDataException(LocalizedFormats.EMPTY_POLYNOMIALS_COEFFICIENTS_ARRAY);
+        }
+        DerivativeStructure result =
+                new DerivativeStructure(t.getFreeParameters(), t.getOrder(), coefficients[n - 1]);
+        for (int j = n - 2; j >= 0; j--) {
+            result = result.multiply(t).add(coefficients[j]);
+        }
+        return result;
+    }
+
     /**
      * Add a polynomial to the instance.
      *
diff --git a/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialSplineFunction.java b/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialSplineFunction.java
index b25ac2d53..ff34f379e 100644
--- a/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialSplineFunction.java
+++ b/src/main/java/org/apache/commons/math3/analysis/polynomials/PolynomialSplineFunction.java
@@ -21,6 +21,8 @@ import java.util.Arrays;
 import org.apache.commons.math3.util.MathArrays;
 import org.apache.commons.math3.analysis.DifferentiableUnivariateFunction;
 import org.apache.commons.math3.analysis.UnivariateFunction;
+import org.apache.commons.math3.analysis.differentiation.DerivativeStructure;
+import org.apache.commons.math3.analysis.differentiation.UnivariateDifferentiable;
 import org.apache.commons.math3.exception.OutOfRangeException;
 import org.apache.commons.math3.exception.NumberIsTooSmallException;
 import org.apache.commons.math3.exception.DimensionMismatchException;
@@ -61,7 +63,7 @@ import org.apache.commons.math3.exception.util.LocalizedFormats;
  *
  * @version $Id$
  */
-public class PolynomialSplineFunction implements DifferentiableUnivariateFunction {
+public class PolynomialSplineFunction implements UnivariateDifferentiable, DifferentiableUnivariateFunction {
     /**
      * Spline segment interval delimiters (knots).
      * Size is n + 1 for n segments.
@@ -168,6 +170,28 @@ public class PolynomialSplineFunction implements DifferentiableUnivariateFunctio
         return new PolynomialSplineFunction(knots, derivativePolynomials);
     }
 
+
+    /** {@inheritDoc}
+     * @since 3.1
+     */
+    public DerivativeStructure value(final DerivativeStructure t) {
+        final double t0 = t.getValue();
+        if (t0 < knots[0] || t0 > knots[n]) {
+            throw new OutOfRangeException(t0, knots[0], knots[n]);
+        }
+        int i = Arrays.binarySearch(knots, t0);
+        if (i < 0) {
+            i = -i - 2;
+        }
+        // This will handle the case where t is the last knot value
+        // There are only n-1 polynomials, so if t is the last knot
+        // then we will use the last polynomial to calculate the value.
+        if ( i >= polynomials.length ) {
+            i--;
+        }
+        return polynomials[i].value(t.subtract(knots[i]));
+    }
+
     /**
      * Get the number of spline segments.
      * It is also the number of polynomials and the number of knot points - 1.