/**
* Copyright (C) 2011 Brian Ferris <bdferris@onebusaway.org>
*
* 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 org.onebusaway.transit_data_federation.impl.probability;
import cern.jet.stat.Probability;
public class HalfNormal {
private static final double SQRT_TWO = Math.sqrt(2.0);
private final double _sigma;
public HalfNormal(double sigma) {
_sigma = sigma;
}
public double cdf(double x) {
if (x < 0)
return 0.0;
return Probability.errorFunction(x / (SQRT_TWO * _sigma));
}
}