1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.numbers.gamma;
18
19 /**
20 * Inverse of the <a href="http://mathworld.wolfram.com/Erfc.html">complementary error function</a>.
21 */
22 public final class InverseErfc {
23 /** Private constructor. */
24 private InverseErfc() {
25 // intentionally empty.
26 }
27
28 /**
29 * Returns the inverse complementary error function.
30 *
31 * <p>Special cases:
32 * <ul>
33 * <li>If the argument is 1, then the result is 0.
34 * <li>If the argument is 0, then the result is positive infinity.
35 * <li>If the argument is 2, then the result is negative infinity.
36 * <li>If the argument is outside the interval {@code [0, 2]}, then the result is nan.
37 * <li>If the argument is nan, then the result is nan.
38 * </ul>
39 *
40 * @param x Value (in {@code [0, 2]})
41 * @return t such that {@code x =} {@link Erfc#value(double) Erfc.value(t)}.
42 */
43 public static double value(double x) {
44 return BoostErf.erfcInv(x);
45 }
46 }