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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.
- IF S='1', set the flag corresponding to the larger of X and Y, subject to the maximum of 4. For example, if X=1 and Y=2, then set A2 = 1, leaving the other flags equal to zero. If X=2 and Y=6, set A4=1, etc.
- IF S is anything else, set the flag corresponding to Y, with the same maximum (ignore X entirely).
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?
- Tags:
- array
- initial values
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The inital values for the array implies RETAIN of those variables.
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The inital values for the array implies RETAIN of those variables.
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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
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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.
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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;
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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.