InverseLinkFunction.java

/*
 * Artificial Intelligence for Humans
 * Volume 2: Nature Inspired Algorithms
 * Java Version
 * http://www.aifh.org
 * http://www.jeffheaton.com
 *
 * Code repository:
 * https://github.com/jeffheaton/aifh
 *
 * Copyright 2014 by Jeff Heaton
 *
 * Licensed 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.
 *
 * For more information on Heaton Research copyrights, licenses
 * and trademarks visit:
 * http://www.heatonresearch.com/copyright
 */
package com.heatonresearch.aifh.general.fns.link;

import com.heatonresearch.aifh.AIFHError;
import com.heatonresearch.aifh.general.fns.Fn;

/**
 * The inverse link function for a GLM.
 * <p/>
 * http://en.wikipedia.org/wiki/Generalized_linear_model
 */
public class InverseLinkFunction implements Fn {

    /**
     * {@inheritDoc}
     */
    @Override
    public double evaluate(final double[] x) {
        if (x.length > 1) {
            throw new AIFHError("The inverse link function can only accept one parameter.");
        }

        return -Math.pow(x[0], -1);
    }
}