SAS：来自数据集的最高变量的输出

Question

I want to assign a new variable from existing highest n variable. So if we have a table that has increasing number of columns -

data have;
input uid $ var1 $ var2 $ var3 $;
datalines;                      
1111    1   0   1
2222    1   0   0
3333    0   0   0
4444    1   1   1
5555    0   0   0
6666    1   1   1
;

I want derive the variable var3 as final_code.

data want;
set have;
final_code = max(of var1-var3);
run;

Above doesn't make sense here as I want only var3 column to remain. Similarly, if var4 is there, I wish to have var4 only.

Does somebody want to help me here ?

Answer 1

If I understand you right, you don't want max of the values but the value from the highest-numbered-variable.

Lots of ways to do this, which way depends on how the variables are named. Here's the easiest, if they're actually named as you say.

data want;
  set have;
  array var[*] var:;
  final_code = var[dim(var)];
run;

Here we make an array out of var: and then choose the last element in the array using dim (to say the size of the array).

Answer 2

I think this is what you are looking for is:

%let n=3
data want;
set have;
var&n = max(of var1-var&n);
drop var1-var%eval(&n-1);
run;

The macro variable &n holds the value of n. This acts as a substitution during the compilation phase of the code.

The DROP statement tells the data step to drop those variable.

The %eval() macro function performs integer math on macro values. So we are dropping 1 through N-1.