SOLR-131476: Add movingMAD Stream Evaluator

solr/solrj/src/java/org/apache/solr/client/solrj/io/Lang.java

@@ -281,6 +281,7 @@ public class Lang {
         .withFunctionName("rtrim", RightShiftEvaluator.class)
         .withFunctionName("repeat", RepeatEvaluator.class)
         .withFunctionName("natural", NaturalEvaluator.class)
+        .withFunctionName("movingMAD", MovingMADEvaluator.class)
 
         // Boolean Stream Evaluators
 

solr/solrj/src/java/org/apache/solr/client/solrj/io/eval/MovingMADEvaluator.java

@@ -0,0 +1,71 @@
+/*
+ * 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.solr.client.solrj.io.eval;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+
+import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
+import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
+
+public class MovingMADEvaluator extends RecursiveNumericEvaluator implements TwoValueWorker {
+  protected static final long serialVersionUID = 1L;
+
+  public MovingMADEvaluator(StreamExpression expression, StreamFactory factory) throws IOException{
+    super(expression, factory);
+  }
+
+  @Override
+  public Object doWork(Object first, Object second) throws IOException{
+    if(null == first){
+      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - null found for the first value",toExpression(constructingFactory)));
+    }
+    if(null == second){
+      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - null found for the second value",toExpression(constructingFactory)));
+    }
+    if(!(first instanceof List<?>)){
+      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - found type %s for the first value, expecting a List",toExpression(constructingFactory), first.getClass().getSimpleName()));
+    }
+    if(!(second instanceof Number)){
+      throw new IOException(String.format(Locale.ROOT,"Invalid expression %s - found type %s for the second value, expecting a Number",toExpression(constructingFactory), first.getClass().getSimpleName()));
+    }
+
+    List<?> values = (List<?>)first;
+    int window = ((Number)second).intValue();
+
+    List<Number> moving = new ArrayList<>();
+    DescriptiveStatistics slider = new DescriptiveStatistics(window);
+    for(Object value : values){
+      slider.addValue(((Number)value).doubleValue());
+      if(slider.getN() >= window){
+        double[] doubles = slider.getValues();
+        double mean = slider.getMean();
+        double total = 0;
+        for(double d : doubles) {
+          total+=Math.abs(d-mean);
+        }
+        moving.add(total/window);
+      }
+    }
+
+    return moving;
+  }
+
+}

solr/solrj/src/test/org/apache/solr/client/solrj/io/TestLang.java

@@ -74,7 +74,7 @@ public class TestLang extends LuceneTestCase {
       "convexHull", "getVertices", "getBaryCenter", "getArea", "getBoundarySize","oscillate",
       "getAmplitude", "getPhase", "getAngularFrequency", "enclosingDisk", "getCenter", "getRadius",
       "getSupportPoints", "pairSort", "log10", "plist", "recip", "pivot", "ltrim", "rtrim", "export",
-      "zplot", "natural", "repeat"};
+      "zplot", "natural", "repeat", "movingMAD"};
 
   @Test
   public void testLang() {

solr/solrj/src/test/org/apache/solr/client/solrj/io/stream/MathExpressionTest.java

@@ -4313,6 +4313,26 @@ public class MathExpressionTest extends SolrCloudTestCase {
     assertEquals((double) out.get(3), 5.5, .0);
   }
 
+  @Test
+  public void testMovingMAD() throws Exception {
+    String cexpr = "movingMAD(array(1,2,3,4,5,6,9), 4)";
+    ModifiableSolrParams paramsLoc = new ModifiableSolrParams();
+    paramsLoc.set("expr", cexpr);
+    paramsLoc.set("qt", "/stream");
+    String url = cluster.getJettySolrRunners().get(0).getBaseUrl().toString()+"/"+COLLECTIONORALIAS;
+    TupleStream solrStream = new SolrStream(url, paramsLoc);
+    StreamContext context = new StreamContext();
+    solrStream.setStreamContext(context);
+    List<Tuple> tuples = getTuples(solrStream);
+    assertTrue(tuples.size() == 1);
+    List<Number> out = (List<Number>)tuples.get(0).get("return-value");
+    assertTrue(out.size()==4);
+    assertEquals((double) out.get(0).doubleValue(), 1, .0);
+    assertEquals((double) out.get(1).doubleValue(), 1, .0);
+    assertEquals((double) out.get(2).doubleValue(), 1, .0);
+    assertEquals((double) out.get(3).doubleValue(), 1.5, .0);
+  }
+
   @Test
   public void testMannWhitney() throws Exception {
     String cexpr = "mannWhitney(array(0.15,0.10,0.11,0.24,0.08,0.08,0.10,0.10,0.10,0.12,0.04,0.07), " +