SAS Do 循环:在循环内使用循环变量来创建滞后变量 [英] SAS Do loops: use loop variable inside the loop to create lagged variables

问题描述

我想创建包含大量滞后的给定变量的滞后值的变量.我怎么能这样做?我尝试以下操作:

I would like to create variables containing lagged values of a given variable for a large number of lags. How could I do this? I try the following:

data out; 
set in;
do i = 1 to 50;
%let j = i;
lag_&j = Lag&j.(x);
end;
run;

如何将循环变量 i 放入宏变量 j 或如何直接使用它来创建适当命名的变量和 Lag 函数?

How can I get the loop variable i into the macro variable j or how to use it directly to create the appropriately named variable and for the Lag function?

推荐答案

Chris J 回答了这个问题，但在这里我将提供我首选的方法.

Chris J answers the question, but here i'll provide my preferred way of doing this.

%macro lagvar(var=,num=);
  %do _iter = 1 %to &num.;
    lag_&_iter. = lag&_iter.(&var.);
  %end;
%mend lagvar;

data out;
  set in;
  %lagvar(var=x,num=50); *semicolon optional here;
run;

这是宏循环的更模块化用法(并且更具可读性，假设您使用智能名称 - 上面没问题，如果您想非常清楚，您可以对名称进行更多操作，当然还可以添加注释).

This is a more modular usage of the macro loop (and more readable, assuming you use intelligent names - the above is okay, you could do even more with the name if you wanted to be very clear, and of course add comments).

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