SAS，按组求和 [英] SAS, sum by group

问题描述

我想通过 var1 计算总和.你能不能用两种方法来计算.SQL 和数据步骤与 if first.var1.

I want to calculate the sum by var1. Could you use two methods to do the calculation. SQL and data step with if first.var1.

data have;
input var1 var2$ var3;
datalines;

1 a 3
1 a 4
1 a 3
2 b 5
2 b 3
3 c 1
;
run;

data want;
input var1 var2 $ var3 sum_by_var1;
datalines;

1 a 3 10
1 a 4 10
1 a 3 10
2 b 5 9
2 b 3 9
3 c 1 9
;
run;

我的两种方式:

下面的代码适用于这个小数据集，但我想知道它是否适用于大数据集，因为很难检查结果.

The code below works on this small data set, but I wonder if it will work on large data sets because it is hard to check the results.

proc sql;
 create table new as 
 select 
 *
 ,sum(var3) as sum_by_var1
 from have
 group by var1
 order by var1
 ;
run;

下面的代码不起作用

data new2;   
   set have;       
   by var1; 
   if first.var1 then
   by_var1 + var3;
run;

推荐答案

要使用需要使用的数据步骤修正计算:

To fix your calculation using the data step you need to use:

1. Retain 关键字，用于计算 var1 的总和，
2. Output 关键字只输出一次 var1 的和；那是到达 var1 的最后一个观察值时，
3. 如果您想要分离的数据，您必须重新连接到您的 Have 表.

1. Retain keyword to calculate the sum by var1,
2. Output keyword to output only once sum by var1 is calculated; that's when reaching the last observation for var1,
3. If you want the segregated data you have to join back to your Have table.

修复:

data new2;   
   set have;       
   by var1; 
   retain sum_by_var1;
   if first.var1 then do; sum_by_var1=0; end;
   sum_by_var1 + var3;
   if last.var1 then do; output; end;
run;

输出:

var1=1 var2=a var3=3 sum_by_var1=10 
var1=2 var2=b var3=3 sum_by_var1=8 
var1=3 var2=c var3=1 sum_by_var1=1 

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