1 /*
2 * Copyright (C) 2023 Alberto Irurueta Carro (alberto@irurueta.com)
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package com.irurueta.numerical.interpolation;
17
18 /**
19 * Inverse Multi-quadric Radial Function Basis implementation.
20 */
21 public class InverseMultiQuadricRadialBasisFunction implements RadialBasisFunction {
22
23 /**
24 * Squared r0 value, which is a scale factor.
25 */
26 private final double r02;
27
28 /**
29 * Constructor.
30 *
31 * @param scale scale factor.
32 */
33 public InverseMultiQuadricRadialBasisFunction(final double scale) {
34 r02 = scale * scale;
35 }
36
37 /**
38 * Constructor.
39 * Uses default scale factor, which is 1.0.
40 */
41 public InverseMultiQuadricRadialBasisFunction() {
42 this(1.0);
43 }
44
45 /**
46 * Evaluates RBF at provided distance between two points.
47 *
48 * @param r distance between two points.
49 * @return result of evaluating RBF.
50 */
51 @Override
52 public double evaluate(double r) {
53 return 1.0 / Math.sqrt((r * r) + r02);
54 }
55 }