I have two variables, X and Y, plus another variable S. X and Y are integers in the range 1-7. S is a character variable that takes the value '1' and some others. I want to create a series of flags, A1-A4, according to these rules.
I first wrote this:
DATA Test;
SET Source;
ARRAY A[4] A1-A4 (0 0 0 0);
IF S = '1' THEN
A[MIN(4,MAX(X,Y))] = 1;
ELSE
A[MIN(4,Y)] = 1;
RUN;
As I read that, it should change only one of the A1-A4 flags for each record. But what I find is that ALL of the values of A1-A4 get set to 1.
If I do this,
DATA Test;
SET Source;
A1 = 0;
A2 = 0;
A3 = 0;
A4 = 0;
ARRAY A[4] A1-A4;
IF S = '1' THEN
A[MIN(4,MAX(X,Y))] = 1;
ELSE
A[MIN(4,Y)] = 1;
RUN;
I get what I want. What is the difference?
The inital values for the array implies RETAIN of those variables.
The inital values for the array implies RETAIN of those variables.
Thanks to all who replied. I seldom use the ability to intialize arrays, and I see that there were implications of doing that which I didn't realize.
Thanks also to those who showed me how to make the code more compact. Those are clever uses of SAS functions. I'm not sure if I will use them. I fear that a few years from now, someone (possibly me) will look at the code and say, "What the heck does that do?" I don't want my code to be more clever than my ability to understand it!
--Dav
ARRAY A[4] A1-A4 (0 0 0 0);
initialises the values only once: when the array is created.
There are 2 cases when array values are not reset in the data step loop: when they are temporary, and when their values are initialised.
If it helps, you can shrink your if clauses:
data source; s="1"; x=3; y=3; output; s="2"; x=1; y=6; output; run; data test; set source; array a[4] (0 0 0 0); a[min(4,max(x,y))]=ifn(s='1',1,0); run;
Side note: The specifiction of an initial value for one array variable implies RETAIN for all variables of the array, including those which are not initialized.
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