smile.validation.FMeasure Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2010 Haifeng Li
*
* 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.
*******************************************************************************/
package smile.validation;
/**
* The F-measure (also F1 score or F-score) considers both the precision p and
* the recall r of the test to compute the score. The F-measure is the harmonic
* mean of precision and recall,
*
* F-measure = 2 * precision * recall / (precision + recall)
*
* where an F-measure reaches its best value at 1 and worst score at 0.:
*
* @author Haifeng Li
*/
public class FMeasure implements ClassificationMeasure {
@Override
public double measure(int[] truth, int[] prediction) {
if (truth.length != prediction.length) {
throw new IllegalArgumentException(String.format("The vector sizes don't match: %d != %d.", truth.length, prediction.length));
}
int tp = 0;
int p = 0;
int pp = 0;
for (int i = 0; i < truth.length; i++) {
if (truth[i] == 1) {
pp++;
}
if (prediction[i] == 1) {
p++;
if (truth[i] == 1) {
tp++;
}
}
}
double precision = (double) tp / p;
double recall = (double) tp / pp;
return 2 * precision * recall / (precision + recall);
}
@Override
public String toString() {
return "F-Measure";
}
}