content: /*
   * 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 io.airlift.stats.cardinality;
  
  public class Stats
  {
      private int count;
      private double mean;
      private double accumulator;
  
      public void add(double value)
      {
          count++;
  
          double delta = value - mean;
          mean += (delta / count);
          accumulator += delta * (value - mean);
      }
  
      public int count()
      {
          return count;
      }
  
      public double mean()
      {
          return mean;
      }
  
      public double stdev()
      {
          return Math.sqrt(accumulator / count);
      }
  
      public static Stats[] array(int size)
      {
          Stats[] result = new Stats[size];
          for (int i = 0; i < size; i++) {
              result[i] = new Stats();
          }
  
          return result;
      }
  }
  