Java tutorial
/* * 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.solr.client.solrj.io.eval; import java.io.IOException; import java.util.Locale; import org.apache.commons.math3.analysis.DifferentiableUnivariateFunction; import org.apache.commons.math3.analysis.UnivariateFunction; import org.apache.solr.client.solrj.io.stream.expr.StreamExpression; import org.apache.solr.client.solrj.io.stream.expr.StreamFactory; public class DerivativeEvaluator extends RecursiveObjectEvaluator implements OneValueWorker { protected static final long serialVersionUID = 1L; public DerivativeEvaluator(StreamExpression expression, StreamFactory factory) throws IOException { super(expression, factory); } @Override public Object doWork(Object value) throws IOException { if (null == value) { throw new IOException(String.format(Locale.ROOT, "Invalid expression %s - null found for the first value", toExpression(constructingFactory))); } if (!(value instanceof VectorFunction)) { throw new IOException(String.format(Locale.ROOT, "Invalid expression %s - found type %s for the first value, expecting a FunctionVector", toExpression(constructingFactory), value.getClass().getSimpleName())); } VectorFunction vectorFunction = (VectorFunction) value; if (!(vectorFunction.getFunction() instanceof DifferentiableUnivariateFunction)) { throw new IOException("Cannot evaluate derivative from parameter."); } DifferentiableUnivariateFunction func = (DifferentiableUnivariateFunction) vectorFunction.getFunction(); double[] x = (double[]) vectorFunction.getFromContext("x"); UnivariateFunction derfunc = func.derivative(); double[] dvalues = new double[x.length]; for (int i = 0; i < x.length; i++) { dvalues[i] = derfunc.value(x[i]); } VectorFunction vf = new VectorFunction(derfunc, dvalues); vf.addToContext("x", x); vf.addToContext("y", vectorFunction.getFromContext("y")); return vf; } }