Java tutorial
/* * 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 com.facebook.presto.operator.aggregation; import com.facebook.presto.spi.block.Block; import com.facebook.presto.spi.type.StandardTypes; import com.google.common.collect.ImmutableList; import org.apache.commons.math3.stat.regression.SimpleRegression; import org.testng.annotations.Test; import java.util.List; import static com.facebook.presto.block.BlockAssertions.createBlockOfReals; import static com.facebook.presto.block.BlockAssertions.createSequenceBlockOfReal; import static com.google.common.base.Preconditions.checkArgument; public class TestRealRegrSlopeAggregation extends AbstractTestAggregationFunction { @Override public Block[] getSequenceBlocks(int start, int length) { return new Block[] { createSequenceBlockOfReal(start, start + length), createSequenceBlockOfReal(start + 2, start + 2 + length) }; } @Override protected String getFunctionName() { return "regr_slope"; } @Override protected List<String> getFunctionParameterTypes() { return ImmutableList.of(StandardTypes.REAL, StandardTypes.REAL); } @Override public Object getExpectedValue(int start, int length) { if (length <= 1) { return null; } SimpleRegression regression = new SimpleRegression(); for (int i = start; i < start + length; i++) { regression.addData(i + 2, i); } return (float) regression.getSlope(); } @Test public void testNonTrivialResult() { testNonTrivialAggregation(new Float[] { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f }, new Float[] { 1.0f, 4.0f, 9.0f, 16.0f, 25.0f }); testNonTrivialAggregation(new Float[] { 1.0f, 4.0f, 9.0f, 16.0f, 25.0f }, new Float[] { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f }); } private void testNonTrivialAggregation(Float[] y, Float[] x) { SimpleRegression regression = new SimpleRegression(); for (int i = 0; i < x.length; i++) { regression.addData(x[i], y[i]); } float expected = (float) regression.getSlope(); checkArgument(Float.isFinite(expected) && expected != 0.0f, "Expected result is trivial"); testAggregation(expected, createBlockOfReals(y), createBlockOfReals(x)); } }