内推法：指根据已知的系列数值推算出一个在已知数值之间的数值. 内推法假定数值之间存在某种明确的关系,不是一种精确的推算法,但可用于估算债券价格和收益率。内推法分三种类型：线性内推法、对数内推法和立方内推法
import java.text.SimpleDateFormat;
import java.util.ArrayList;import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;
import java.util.Random;
/**
* 计算一定日期内缺失的日期
* @author Administrator
*
*/
public class Chazhi {
static List<Meter> aList = new ArrayList<Meter>();
static {
Random r = new Random();
int temp = 0, temp2;
List<Integer> idList = new ArrayList<Integer>();
idList.add(2);
idList.add(3);
idList.add(6);
for (int i = 1, j = i + 1; i < 10; j++, i++) {
Date dat = null;
Calendar cd = Calendar.getInstance();
cd.add(Calendar.DATE, i);
dat = cd.getTime();
if (idList.contains(i)) {
continue;
}
if (i == 1) {
temp = i + r.nextInt(10);
} else {
temp += i + r.nextInt(10);
}
aList.add(new Meter("meter0", dat, temp));
}
}
static SimpleDateFormat dformat = new SimpleDateFormat("yyyy-MM-dd");
public static void main(String[] args) {
//System.out.println(daysBetween("2017-05-22", "2017-05-23"));
List<Meter> bList = new ArrayList<Meter>();
//第一步补缺失的日期，把日期补全，并且默认值为0
System.out.println("原始值：");
for (int i = 0; i < aList.size(); i++) {
Meter m1 = aList.get(i);
bList.add(m1);
System.out.println(m1.getMeterNo() + "-" + dformat.format(m1.getDay()) + "-" + m1.getVal());
if (i < aList.size() - 1) {
Meter m2 = aList.get(i + 1);
// 日期是连续的，正确
if (daysBetween(dformat.format(m1.getDay()), dformat.format(m2.getDay())) == 1) {
} else {
//相差天数,相差几天就补几天
int d = daysBetween(dformat.format(m1.getDay()), dformat.format(m2.getDay()));
for(int a=1;a<d;a++){
// 说明有缺失日期，需要补值
Calendar calendar = new GregorianCalendar();
calendar.setTime(m1.getDay());
calendar.add(calendar.DATE, a);// 把日期往后增加一天.整数往后推,负数往前移动
// calendar.getTime(); //这个时间就是日期往后推一天的结果
Meter e = new Meter(m1.getMeterNo(), calendar.getTime(), 0);
bList.add(e);
}
}
//System.out.println(daysBetween(dformat.format(m1.getDay()), dformat.format(m2.getDay())));
}
}
// 补缺日期后的值
//第二步 计算缺失值上下的已知值间的斜率
System.out.println("日期补缺后的值========");
System.out.println("计算缺失值上下的已知值间的斜率");
for (int a = 0; a < bList.size(); a++) {
Meter m3 = bList.get(a);
System.out.println(m3.getMeterNo() + "-" + dformat.format(m3.getDay()) + "-" + m3.getVal());
//如果值为0表示缺失值
if(a!=0 && m3.getVal()==0){
//如果不是第一条或者最后一条为0,就查找相邻的两个有值的数据
Meter m3_1 = bList.get(a-1);
Meter m3_2 = bList.get(a+1);
//k = (b2 - b1)/(n + 1) n 为缺失数据的个数
int k = (m3_2.getVal()-m3_1.getVal())/(1 + 1) ;
//步骤二：计算对应的缺失值
//a(i) = b1 + k * i
m3.setVal(m3_1.getVal()+k*a);
}
}
System.out.println("补缺日期和值后的最终结果");
//// 补缺日期和值后的最终结果
for (int a = 0; a < bList.size(); a++) {
Meter m4 = bList.get(a);
System.out.println(m4.getMeterNo() + "-" + dformat.format(m4.getDay()) + "-" + m4.getVal());
}
}
/**
* 返回两个string类型日期之间相差的天数
*
* @param smdate
* @param bdate
* @return
*/
public static int daysBetween(String smdate, String bdate) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Calendar cal = Calendar.getInstance();
long time1 = 0;
long time2 = 0;
try {
cal.setTime(sdf.parse(smdate));
time1 = cal.getTimeInMillis();
cal.setTime(sdf.parse(bdate));
time2 = cal.getTimeInMillis();
} catch (Exception e) {
e.printStackTrace();
}
long between_days = (time2 - time1) / (1000 * 3600 * 24);
return Integer.parseInt(String.valueOf(between_days));
}
}