Index: ml/src/main/java/org/apache/hama/ml/math/FunctionFactory.java =================================================================== --- ml/src/main/java/org/apache/hama/ml/math/FunctionFactory.java (revision 1502033) +++ ml/src/main/java/org/apache/hama/ml/math/FunctionFactory.java (working copy) @@ -30,10 +30,13 @@ * @return */ public static DoubleFunction createDoubleFunction(String functionName) { - if (functionName.equals(Sigmoid.class.getSimpleName())) { + if (functionName.equalsIgnoreCase(Sigmoid.class.getSimpleName())) { return new Sigmoid(); - } else if (functionName.equals(Tanh.class.getSimpleName())) { + } else if (functionName.equalsIgnoreCase(Tanh.class.getSimpleName())) { return new Tanh(); + } else if (functionName.equalsIgnoreCase(IdentityFunction.class + .getSimpleName())) { + return new IdentityFunction(); } throw new IllegalArgumentException(String.format( @@ -48,9 +51,10 @@ */ public static DoubleDoubleFunction createDoubleDoubleFunction( String functionName) { - if (functionName.equals(SquaredError.class.getSimpleName())) { + if (functionName.equalsIgnoreCase(SquaredError.class.getSimpleName())) { return new SquaredError(); - } else if (functionName.equals(CrossEntropy.class.getSimpleName())) { + } else if (functionName + .equalsIgnoreCase(CrossEntropy.class.getSimpleName())) { return new CrossEntropy(); } Index: ml/src/main/java/org/apache/hama/ml/math/IdentityFunction.java =================================================================== --- ml/src/main/java/org/apache/hama/ml/math/IdentityFunction.java (revision 0) +++ ml/src/main/java/org/apache/hama/ml/math/IdentityFunction.java (working copy) @@ -0,0 +1,36 @@ +/** + * 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.hama.ml.math; + +/** + * The identity function f(x) = x. + * + */ +public class IdentityFunction extends DoubleFunction { + + @Override + public double apply(double value) { + return value; + } + + @Override + public double applyDerivative(double value) { + return 0; + } + +}