| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.apache.commons.math4.legacy.analysis.interpolation; |
| |
| import org.apache.commons.math4.legacy.analysis.MultivariateFunction; |
| import org.apache.commons.math4.legacy.core.jdkmath.AccurateMath; |
| import org.junit.Assert; |
| import org.junit.Test; |
| |
| /** |
| * Test case for the {@link MicrosphereProjectionInterpolator |
| * "microsphere projection"} interpolator. |
| */ |
| public final class MicrosphereProjectionInterpolatorTest { |
| /** |
| * Test of interpolator for a plane. |
| * <p> |
| * y = 2 x<sub>1</sub> - 3 x<sub>2</sub> + 5 |
| */ |
| @Test |
| public void testLinearFunction2D() { |
| MultivariateFunction f = new MultivariateFunction() { |
| @Override |
| public double value(double[] x) { |
| if (x.length != 2) { |
| throw new IllegalArgumentException(); |
| } |
| return 2 * x[0] - 3 * x[1] + 5; |
| } |
| }; |
| |
| final double darkFraction = 0.5; |
| final double darkThreshold = 1e-2; |
| final double background = Double.NaN; |
| final double exponent = 1.1; |
| final boolean shareSphere = true; |
| final double noInterpolationTolerance = Math.ulp(1d); |
| |
| // N-dimensional interpolator. |
| final MultivariateInterpolator interpolator |
| = new MicrosphereProjectionInterpolator(2, 500, |
| darkFraction, |
| darkThreshold, |
| background, |
| exponent, |
| shareSphere, |
| noInterpolationTolerance); |
| |
| // 2D interpolator. |
| final MultivariateInterpolator interpolator2D |
| = new MicrosphereProjectionInterpolator(new InterpolatingMicrosphere2D(16, |
| darkFraction, |
| darkThreshold, |
| background), |
| exponent, |
| shareSphere, |
| noInterpolationTolerance); |
| |
| final double min = -1; |
| final double max = 1; |
| final double range = max - min; |
| final int res = 5; |
| final int n = res * res; // Number of sample points. |
| final int dim = 2; |
| double[][] x = new double[n][dim]; |
| double[] y = new double[n]; |
| int index = 0; |
| for (int i = 0; i < res; i++) { |
| final double x1Val = toCoordinate(min, range, res, i); |
| for (int j = 0; j < res; j++) { |
| final double x2Val = toCoordinate(min, range, res, j); |
| x[index][0] = x1Val; |
| x[index][1] = x2Val; |
| y[index] = f.value(x[index]); |
| ++index; |
| } |
| } |
| |
| final MultivariateFunction p = interpolator.interpolate(x, y); |
| final MultivariateFunction p2D = interpolator2D.interpolate(x, y); |
| |
| double[] c = new double[dim]; |
| double expected; |
| double result; |
| double result2D; |
| |
| final int sampleIndex = 2; |
| c[0] = x[sampleIndex][0]; |
| c[1] = x[sampleIndex][1]; |
| expected = f.value(c); |
| result = p.value(c); |
| result2D = p2D.value(c); |
| Assert.assertEquals("on sample point (exact)", expected, result2D, AccurateMath.ulp(1d)); |
| Assert.assertEquals("on sample point (ND vs 2D)", result2D, result, AccurateMath.ulp(1d)); |
| |
| // Interpolation. |
| c[0] = 0.654321; |
| c[1] = -0.345678; |
| expected = f.value(c); |
| result = p.value(c); |
| result2D = p2D.value(c); |
| Assert.assertEquals("interpolation (exact)", expected, result2D, 1e-1); |
| Assert.assertEquals("interpolation (ND vs 2D)", result2D, result, 1e-1); |
| |
| // Extrapolation. |
| c[0] = 0 - 1e-2; |
| c[1] = 1 + 1e-2; |
| expected = f.value(c); |
| result = p.value(c); |
| result2D = p2D.value(c); |
| Assert.assertFalse(Double.isNaN(result)); |
| Assert.assertFalse(Double.isNaN(result2D)); |
| Assert.assertEquals("extrapolation (exact)", expected, result2D, 1e-1); |
| Assert.assertEquals("extrapolation (ND vs 2D)", result2D, result, 1e-2); |
| |
| // Far away. |
| c[0] = 20; |
| c[1] = -30; |
| result = p.value(c); |
| Assert.assertTrue(result + " should be NaN", Double.isNaN(result)); |
| result2D = p2D.value(c); |
| Assert.assertTrue(result2D + " should be NaN", Double.isNaN(result2D)); |
| } |
| |
| /** |
| * @param min Minimum of the coordinate range. |
| * @param range Extent of the coordinate interval. |
| * @param res Number of pixels. |
| * @param pixel Pixel index. |
| */ |
| private static double toCoordinate(double min, |
| double range, |
| int res, |
| int pixel) { |
| return pixel * range / (res - 1) + min; |
| } |
| } |