content: /*******************************************************************************
   * Copyright 2017 Bstek
   *
   * 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.bstek.ureport.expression.function.math;
  
  import com.bstek.ureport.build.Context;
  import com.bstek.ureport.expression.model.data.ExpressionData;
  import com.bstek.ureport.model.Cell;
  
  import java.math.BigDecimal;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * 求中位数
   * @author
   * @since 1月23日
   */
  public class MedianFunction extends MathFunction {
  
  	@Override
  	public Object execute(List<ExpressionData<?>> dataList, Context context,Cell currentCell) {
  		List<BigDecimal> list=buildDataList(dataList);
  		int size=list.size();
  		if(size==1){
  			return list.get(0);
  		}else if(size==2){
  			BigDecimal data=list.get(0).add(list.get(1));
  			return data.divide(new BigDecimal(2),8,BigDecimal.ROUND_HALF_UP);
  		}
  		Collections.sort(list);
  		int mode=size % 2;
  		if(mode==0){
  			int half = size / 2;
  			int start=half-1;
  			BigDecimal data=list.get(start).add(list.get(half));
  			return data.divide(new BigDecimal(2),8,BigDecimal.ROUND_HALF_UP);
  		}else{
  			int half=size / 2;
  			return list.get(half);
  		}
  	}
  
  	@Override
  	public String name() {
  		return "median";
  	}
  }
  