/*
 * Copyright (c) 2018, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 * WSO2 Inc. 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 io.siddhi.extension.execution.streamingml.bayesian.util;

import java.io.Serializable;

/**
 * performs prequential evaluation for classification.
 */
public class PrequentialEvaluation implements Serializable {

    private static final long serialVersionUID = -7152382901763677063L;
    private double numberOfSamples;
    private double numberOfErrors;

    public PrequentialEvaluation() {
        numberOfSamples = 0;
        numberOfErrors = 0;
    }

    public double evaluate(int trueLabel, int predictedLabel) {
        numberOfSamples += 1;

        if (trueLabel != predictedLabel) {
            numberOfErrors += 1;
        }

        return 1 - (numberOfErrors / numberOfSamples);
    }
}
