Raymond | dee0849 | 2015-04-02 10:43:13 -0700 | [diff] [blame] | 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.math.analysis.interpolation; |
| 18 | |
| 19 | import org.apache.commons.math.exception.DimensionMismatchException; |
| 20 | import org.apache.commons.math.exception.NoDataException; |
| 21 | import org.apache.commons.math.MathException; |
| 22 | import org.apache.commons.math.util.MathUtils; |
| 23 | |
| 24 | /** |
| 25 | * Generates a tricubic interpolating function. |
| 26 | * |
| 27 | * @version $Revision$ $Date$ |
| 28 | * @since 2.2 |
| 29 | */ |
| 30 | public class TricubicSplineInterpolator |
| 31 | implements TrivariateRealGridInterpolator { |
| 32 | /** |
| 33 | * {@inheritDoc} |
| 34 | */ |
| 35 | public TricubicSplineInterpolatingFunction interpolate(final double[] xval, |
| 36 | final double[] yval, |
| 37 | final double[] zval, |
| 38 | final double[][][] fval) |
| 39 | throws MathException { |
| 40 | if (xval.length == 0 || yval.length == 0 || zval.length == 0 || fval.length == 0) { |
| 41 | throw new NoDataException(); |
| 42 | } |
| 43 | if (xval.length != fval.length) { |
| 44 | throw new DimensionMismatchException(xval.length, fval.length); |
| 45 | } |
| 46 | |
| 47 | MathUtils.checkOrder(xval); |
| 48 | MathUtils.checkOrder(yval); |
| 49 | MathUtils.checkOrder(zval); |
| 50 | |
| 51 | final int xLen = xval.length; |
| 52 | final int yLen = yval.length; |
| 53 | final int zLen = zval.length; |
| 54 | |
| 55 | // Samples, re-ordered as (z, x, y) and (y, z, x) tuplets |
| 56 | // fvalXY[k][i][j] = f(xval[i], yval[j], zval[k]) |
| 57 | // fvalZX[j][k][i] = f(xval[i], yval[j], zval[k]) |
| 58 | final double[][][] fvalXY = new double[zLen][xLen][yLen]; |
| 59 | final double[][][] fvalZX = new double[yLen][zLen][xLen]; |
| 60 | for (int i = 0; i < xLen; i++) { |
| 61 | if (fval[i].length != yLen) { |
| 62 | throw new DimensionMismatchException(fval[i].length, yLen); |
| 63 | } |
| 64 | |
| 65 | for (int j = 0; j < yLen; j++) { |
| 66 | if (fval[i][j].length != zLen) { |
| 67 | throw new DimensionMismatchException(fval[i][j].length, zLen); |
| 68 | } |
| 69 | |
| 70 | for (int k = 0; k < zLen; k++) { |
| 71 | final double v = fval[i][j][k]; |
| 72 | fvalXY[k][i][j] = v; |
| 73 | fvalZX[j][k][i] = v; |
| 74 | } |
| 75 | } |
| 76 | } |
| 77 | |
| 78 | final BicubicSplineInterpolator bsi = new BicubicSplineInterpolator(); |
| 79 | |
| 80 | // For each line x[i] (0 <= i < xLen), construct a 2D spline in y and z |
| 81 | final BicubicSplineInterpolatingFunction[] xSplineYZ |
| 82 | = new BicubicSplineInterpolatingFunction[xLen]; |
| 83 | for (int i = 0; i < xLen; i++) { |
| 84 | xSplineYZ[i] = bsi.interpolate(yval, zval, fval[i]); |
| 85 | } |
| 86 | |
| 87 | // For each line y[j] (0 <= j < yLen), construct a 2D spline in z and x |
| 88 | final BicubicSplineInterpolatingFunction[] ySplineZX |
| 89 | = new BicubicSplineInterpolatingFunction[yLen]; |
| 90 | for (int j = 0; j < yLen; j++) { |
| 91 | ySplineZX[j] = bsi.interpolate(zval, xval, fvalZX[j]); |
| 92 | } |
| 93 | |
| 94 | // For each line z[k] (0 <= k < zLen), construct a 2D spline in x and y |
| 95 | final BicubicSplineInterpolatingFunction[] zSplineXY |
| 96 | = new BicubicSplineInterpolatingFunction[zLen]; |
| 97 | for (int k = 0; k < zLen; k++) { |
| 98 | zSplineXY[k] = bsi.interpolate(xval, yval, fvalXY[k]); |
| 99 | } |
| 100 | |
| 101 | // Partial derivatives wrt x and wrt y |
| 102 | final double[][][] dFdX = new double[xLen][yLen][zLen]; |
| 103 | final double[][][] dFdY = new double[xLen][yLen][zLen]; |
| 104 | final double[][][] d2FdXdY = new double[xLen][yLen][zLen]; |
| 105 | for (int k = 0; k < zLen; k++) { |
| 106 | final BicubicSplineInterpolatingFunction f = zSplineXY[k]; |
| 107 | for (int i = 0; i < xLen; i++) { |
| 108 | final double x = xval[i]; |
| 109 | for (int j = 0; j < yLen; j++) { |
| 110 | final double y = yval[j]; |
| 111 | dFdX[i][j][k] = f.partialDerivativeX(x, y); |
| 112 | dFdY[i][j][k] = f.partialDerivativeY(x, y); |
| 113 | d2FdXdY[i][j][k] = f.partialDerivativeXY(x, y); |
| 114 | } |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | // Partial derivatives wrt y and wrt z |
| 119 | final double[][][] dFdZ = new double[xLen][yLen][zLen]; |
| 120 | final double[][][] d2FdYdZ = new double[xLen][yLen][zLen]; |
| 121 | for (int i = 0; i < xLen; i++) { |
| 122 | final BicubicSplineInterpolatingFunction f = xSplineYZ[i]; |
| 123 | for (int j = 0; j < yLen; j++) { |
| 124 | final double y = yval[j]; |
| 125 | for (int k = 0; k < zLen; k++) { |
| 126 | final double z = zval[k]; |
| 127 | dFdZ[i][j][k] = f.partialDerivativeY(y, z); |
| 128 | d2FdYdZ[i][j][k] = f.partialDerivativeXY(y, z); |
| 129 | } |
| 130 | } |
| 131 | } |
| 132 | |
| 133 | // Partial derivatives wrt x and wrt z |
| 134 | final double[][][] d2FdZdX = new double[xLen][yLen][zLen]; |
| 135 | for (int j = 0; j < yLen; j++) { |
| 136 | final BicubicSplineInterpolatingFunction f = ySplineZX[j]; |
| 137 | for (int k = 0; k < zLen; k++) { |
| 138 | final double z = zval[k]; |
| 139 | for (int i = 0; i < xLen; i++) { |
| 140 | final double x = xval[i]; |
| 141 | d2FdZdX[i][j][k] = f.partialDerivativeXY(z, x); |
| 142 | } |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | // Third partial cross-derivatives |
| 147 | final double[][][] d3FdXdYdZ = new double[xLen][yLen][zLen]; |
| 148 | for (int i = 0; i < xLen ; i++) { |
| 149 | final int nI = nextIndex(i, xLen); |
| 150 | final int pI = previousIndex(i); |
| 151 | for (int j = 0; j < yLen; j++) { |
| 152 | final int nJ = nextIndex(j, yLen); |
| 153 | final int pJ = previousIndex(j); |
| 154 | for (int k = 0; k < zLen; k++) { |
| 155 | final int nK = nextIndex(k, zLen); |
| 156 | final int pK = previousIndex(k); |
| 157 | |
| 158 | // XXX Not sure about this formula |
| 159 | d3FdXdYdZ[i][j][k] = (fval[nI][nJ][nK] - fval[nI][pJ][nK] - |
| 160 | fval[pI][nJ][nK] + fval[pI][pJ][nK] - |
| 161 | fval[nI][nJ][pK] + fval[nI][pJ][pK] + |
| 162 | fval[pI][nJ][pK] - fval[pI][pJ][pK]) / |
| 163 | ((xval[nI] - xval[pI]) * (yval[nJ] - yval[pJ]) * (zval[nK] - zval[pK])) ; |
| 164 | } |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | // Create the interpolating splines |
| 169 | return new TricubicSplineInterpolatingFunction(xval, yval, zval, fval, |
| 170 | dFdX, dFdY, dFdZ, |
| 171 | d2FdXdY, d2FdZdX, d2FdYdZ, |
| 172 | d3FdXdYdZ); |
| 173 | } |
| 174 | |
| 175 | /** |
| 176 | * Compute the next index of an array, clipping if necessary. |
| 177 | * It is assumed (but not checked) that {@code i} is larger than or equal to 0}. |
| 178 | * |
| 179 | * @param i Index |
| 180 | * @param max Upper limit of the array |
| 181 | * @return the next index |
| 182 | */ |
| 183 | private int nextIndex(int i, int max) { |
| 184 | final int index = i + 1; |
| 185 | return index < max ? index : index - 1; |
| 186 | } |
| 187 | /** |
| 188 | * Compute the previous index of an array, clipping if necessary. |
| 189 | * It is assumed (but not checked) that {@code i} is smaller than the size of the array. |
| 190 | * |
| 191 | * @param i Index |
| 192 | * @return the previous index |
| 193 | */ |
| 194 | private int previousIndex(int i) { |
| 195 | final int index = i - 1; |
| 196 | return index >= 0 ? index : 0; |
| 197 | } |
| 198 | } |