SOLR-12634: Add gaussfit Stream Evaluator

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

@@ -247,6 +247,7 @@ public class Lang {
         .withFunctionName("getValue", GetValueEvaluator.class)
         .withFunctionName("setValue", SetValueEvaluator.class)
         .withFunctionName("knnRegress", KnnRegressionEvaluator.class)
+        .withFunctionName("gaussfit", GaussFitEvaluator.class)
 
         // Boolean Stream Evaluators
 

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

@@ -0,0 +1,91 @@
+/*
+ * 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.List;
+import java.util.ArrayList;
+
+import org.apache.commons.math3.analysis.function.Gaussian;
+import org.apache.commons.math3.fitting.GaussianCurveFitter;
+import org.apache.commons.math3.fitting.WeightedObservedPoints;
+import org.apache.commons.math3.fitting.WeightedObservedPoint;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
+import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
+
+public class GaussFitEvaluator extends RecursiveNumericEvaluator implements ManyValueWorker {
+  protected static final long serialVersionUID = 1L;
+
+  public GaussFitEvaluator(StreamExpression expression, StreamFactory factory) throws IOException{
+    super(expression, factory);
+  }
+
+  @Override
+  public Object doWork(Object... objects) throws IOException{
+
+    if(objects.length >= 3) {
+      throw new IOException("gaussfit function takes a maximum of 2 arguments.");
+    }
+
+    Object first = objects[0];
+
+    double[] x = null;
+    double[] y = null;
+
+    if(objects.length == 1) {
+      //Only the y values passed
+
+      y = ((List) first).stream().mapToDouble(value -> ((Number) value).doubleValue()).toArray();
+      x = new double[y.length];
+      for(int i=0; i<y.length; i++) {
+        x[i] = i;
+      }
+
+    } else if(objects.length == 2) {
+      // x and y passed
+      Object second = objects[1];
+      x = ((List) first).stream().mapToDouble(value -> ((Number) value).doubleValue()).toArray();
+      y = ((List) second).stream().mapToDouble(value -> ((Number) value).doubleValue()).toArray();
+
+
+    }
+
+    GaussianCurveFitter curveFitter = GaussianCurveFitter.create();
+
+    WeightedObservedPoints points = new WeightedObservedPoints();
+    for(int i=0; i<x.length; i++) {
+      points.add(x[i], y[i]);
+    }
+
+    List<WeightedObservedPoint> pointList = points.toList();
+
+    double[] guess = new GaussianCurveFitter.ParameterGuesser(pointList).guess();
+    curveFitter = curveFitter.withStartPoint(guess);
+
+    double[] coef = curveFitter.fit(pointList);
+    Gaussian gaussian = new Gaussian(coef[0], coef[1], coef[2]);
+    List list = new ArrayList();
+    for(double xvalue : x) {
+      double yvalue= gaussian.value(xvalue);
+      list.add(yvalue);
+    }
+
+    return new VectorFunction(gaussian, list);
+  }
+}

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

@@ -69,7 +69,7 @@ public class TestLang extends LuceneTestCase {
        TemporalEvaluatorDayOfQuarter.FUNCTION_NAME, "abs", "add", "div", "mult", "sub", "log", "pow",
       "mod", "ceil", "floor", "sin", "asin", "sinh", "cos", "acos", "cosh", "tan", "atan", "tanh", "round", "sqrt",
       "cbrt", "coalesce", "uuid", "if", "convert", "valueAt", "memset", "fft", "ifft", "euclidean","manhattan",
-      "earthMovers", "canberra", "chebyshev", "ones", "zeros", "setValue", "getValue", "knnRegress"};
+      "earthMovers", "canberra", "chebyshev", "ones", "zeros", "setValue", "getValue", "knnRegress", "gaussfit"};
 
   @Test
   public void testLang() {

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

@@ -3465,6 +3465,52 @@ public class MathExpressionTest extends SolrCloudTestCase {
     assertEquals(prediction.doubleValue(), 87.20000076, 0);
   }
 
+  @Test
+  public void testGaussfit() throws Exception {
+    String cexpr = "let(echo=true, " +
+        "x=array(79.56,81.32,82.82,84.64,86.18,87.89,89.53,91.14,92.8,94.43,96.08,97.72,99.37,101,102.66,104.3,105.94,107.59,109.23,110.87,112.52,114.13,115.82,117.44,119.27), " +
+        "y=array(3, 3, 26, 54, 139, 344, 685, 1289, 2337, 3593, 4781, 5964, 6538, 6357, 5705, 4548, 3280, 2058, 1191, 649, 285, 112, 34, 18, 7)," +
+        "g=gaussfit(x,y))";
+
+    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> predictions = (List<Number>)tuples.get(0).get("g");
+    assertEquals(predictions.size(), 25);
+    assertEquals(predictions.get(0).doubleValue(), 1.5217511259930976, 0);
+    assertEquals(predictions.get(1).doubleValue(), 6.043059526517849, 0);
+    assertEquals(predictions.get(2).doubleValue(), 17.74876254851105, 0);
+    assertEquals(predictions.get(3).doubleValue(), 58.12355990996735, 0);
+    assertEquals(predictions.get(4).doubleValue(), 142.98079858358975, 0);
+    assertEquals(predictions.get(5).doubleValue(), 347.5571069372449, 0);
+    assertEquals(predictions.get(6).doubleValue(), 729.8016076579886, 0);
+    assertEquals(predictions.get(7).doubleValue(), 1361.3981561397804, 0);
+    assertEquals(predictions.get(8).doubleValue(), 2322.566306687647, 0);
+    assertEquals(predictions.get(9).doubleValue(), 3524.6949840829216, 0);
+    assertEquals(predictions.get(10).doubleValue(), 4824.273031596218, 0);
+    assertEquals(predictions.get(11).doubleValue(), 5915.519574509397, 0);
+    assertEquals(predictions.get(12).doubleValue(),  6514.552728035438, 0);
+    assertEquals(predictions.get(13).doubleValue(), 6438.3295998729845, 0);
+    assertEquals(predictions.get(14).doubleValue(), 5702.59200814961, 0);
+    assertEquals(predictions.get(15).doubleValue(), 4538.7945530007, 0);
+    assertEquals(predictions.get(16).doubleValue(), 3243.606591784876, 0);
+    assertEquals(predictions.get(17).doubleValue(), 2074.9937785806937, 0);
+    assertEquals(predictions.get(18).doubleValue(), 1194.697766441063, 0);
+    assertEquals(predictions.get(19).doubleValue(), 617.6162726398896, 0);
+    assertEquals(predictions.get(20).doubleValue(), 285.248193084953, 0);
+    assertEquals(predictions.get(21).doubleValue(), 120.84133189889134, 0);
+    assertEquals(predictions.get(22).doubleValue(), 43.87052382491055, 0);
+    assertEquals(predictions.get(23).doubleValue(), 14.918461016939522, 0);
+    assertEquals(predictions.get(24).doubleValue(), 3.887269101204326, 0);
+  }
+
+
   @Test
   public void testPlot() throws Exception {
     String cexpr = "let(a=array(3,2,3), plot(type=scatter, x=a, y=array(5,6,3)))";