按组复制SAS中的值

Question

我有一个数据集，其中包含一个测量和它收集的具体日期。我想在几天之间复制这些值，直到最后一天。例如，以下是复制数据之前的数据：

           Measurement    Day
Subject1   .85            -1
Subject1   .86            1            
Subject1   .91            7            
Subject1   .83            9            
Subject2   .77            0            
Subject2   .82            5            
Subject2   .86            12           

我想修改上面的数据集，如下所示：

           Measurement    Day
Subject1   .85            -1
Subject1   .85            0
Subject1   .86            1
Subject1   .86            2
Subject1   .86            3
Subject1   .86            4
Subject1   .86            5 
Subject1   .86            6           
Subject1   .91            7
Subject1   .91            8            
Subject1   .83            9            
Subject2   .77            0
Subject2   .77            1
Subject2   .77            2
Subject2   .77            3
Subject2   .77            4       
Subject2   .82            5          
Subject2   .82            6
Subject2   .82            7     
Subject2   .82            8     
Subject2   .82            9     
Subject2   .82            10
Subject2   .82            11                      
Subject2   .86            12           

Answer 1

考虑使用辅助数据集展开数据，然后使用左联接merge并进行前向填充。

data helper;
    set input (keep = Subject Day);
    by Subject;
    if not first.Subject and last.Subject;

    max_day = max(Day);
    day = 0;
    do until(day > max_day);
      output;
      day + 1;
    end;

    drop max_day;
run;

data output;
    merge helper (in=h)
          input (in=i);
    if h;
    by Subject Day;

    retain _k;
    if not missing(Measurement) then _k=Measurement;
    else if missing(Measurement) then Measurement=_k;

    if not missing(Measurement);
    drop _k;
run;

数据

data input;
    infile datalines delimiter=',' DSD; 
    length subject $ 10;

    input subject measurement day;
    datalines;
Subject1,.86,1 
Subject1,.91,7 
Subject1,.83,9 
Subject2,.77,0 
Subject2,.82,5 
Subject2,.86,12
;

输出

Obs  subject   day   measurement 
1   Subject1     1          0.86 
2   Subject1     2          0.86 
3   Subject1     3          0.86 
4   Subject1     4          0.86 
5   Subject1     5          0.86 
6   Subject1     6          0.86 
7   Subject1     7          0.91 
8   Subject1     8          0.91 
9   Subject1     9          0.83 
10  Subject2     0          0.77 
11  Subject2     1          0.77 
12  Subject2     2          0.77 
13  Subject2     3          0.77 
14  Subject2     4          0.77 
15  Subject2     5          0.82 
16  Subject2     6          0.82 
17  Subject2     7          0.82 
18  Subject2     8          0.82 
19  Subject2     9          0.82 
20  Subject2     10         0.82 
21  Subject2     11         0.82 
22  Subject2     12         0.86