How to call macro variable within a looping code

[stataq]

Hello,

I would like to know whether it is possible to call marco variables with a looping code. Please see example below:

when i=1, I would like to get:  _inval{1}=put( _invars{1},&_width1). 

Current codes won't work.

  data df1;
	a = .; b=1; c=1; output;
	a = 1; b=.; c=1; output;
	a = 1; b=1; c=.; output;
run; 

%let _width1=3.1;
%let _width2=3.2;
%let _width3=3.3;
data want ;
set df1;
  array _invars{3} a b c;
  array _inval{3} $16 ;

  do i=1 to 3.;
  	 _inval{i}=put( _invars{i},&_widthi)	; /*I want to use &_width(i) where i change with i in looping setting */
  end;		
 run ;

[PeterClemmensen]

This is a classic SAS macro issue of timing. There are two main things you need to change in your code.

1. Use the PUTN Function instead of the PUT Function. The PUTN Function enables you to specify a numeric format at run time. The Put Function does so at compile time, i.e. before the loop executes. 
2. Use the Symget Function in the Data Step to retrieve the value of the macro variable during DATA step execution (not when it compiles).

I changed the input values a bit, to make the result clearer. Feel free to ask.

data df1;
   a = .;     b=1.235; c=1.234; output;
   a = 1.234; b=.;     c=1.234; output;
   a = 1.234; b=1.234; c=.;     output;
run; 

%let _width1=5.1;
%let _width2=5.2;
%let _width3=5.3;

data want ;
   set df1;
   array _invars{3} a b c;
   array _inval{3} $16 ;

   do i = 1 to 3;
      f = symget(cats('_width', i));
      _inval{i}=putn(_invars{i},  f);
   end;     
run;

Result:

a      b      c      _inval1  _inval2  _inval3  i  f
.      1.235  1.234  .        1.24     1.234    4  5.3
1.234  .      1.234  1.2      .        1.234    4  5.3
1.234  1.234  .      1.2      1.23     .        4  5.3

[yabwon · Accepted solution]

I'd say, with OP setup there is no need for macro variables. 

The PUTN which @PeterClemmensen mentioned is all is needed:

data df1;
   a = .;     b=1.235; c=1.234; output;
   a = 1.234; b=.;     c=1.234; output;
   a = 1.234; b=1.234; c=.;     output;
run; 

data want ;
   set df1;
   array _invars{3} a b c;
   array _inval{3} $16 ;

   do i = 1 to 3;
      _inval{i}=putn(_invars{i},  cats("5.",i)); /* build "5.i" text */
   end;     

   put _all_;
run;

Bart

[stataq]

@PeterClemmensen Thanks so much!👍Can we do 

putn(_invars{i},  &_width1.)

directly? I got error message for "expecting a format" 😅

One question might be very silly. How can I tell when an 'i' will change base on the looping i setup?  I was hoping the i in &widthi will change when I do looping. Could you guide me on this? Thanks.

[yabwon]

You have an error because PUTN() function (go to see its documentation: https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.5/lefunctionsref/p12zqzvwx4dv6kn1p9crijxswolk.h... , unfortunatell the description there in vague)

expects a string constant or a character variable/expression which provides format name.

For example if 

%let _width1=best32.20;

then your code should be:

/* option 1 */
putn(_invars{i},  "&_width1.")

/* option 2 */
putn(_invars{i},  symget("_width1"))

Basically, think about it that you want to have:

putn(variable, "format-name.")

/* or */
xxx="format-name.";
putn(variable, xxx)

Bart

[Tom]

---

@stataq wrote:

@PeterClemmensen Thanks so much!👍Can we do 

putn(_invars{i},  &_width1.)

directly? I got error message for "expecting a format" 😅

One question might be very silly. How can I tell when an 'i' will change base on the looping i setup?  I was hoping the i in &widthi will change when I do looping. Could you guide me on this? Thanks.

---

Remember that the macro processor is a PRE processor.  The results after the macro processor has finished needs to be valid SAS code.

So what value did _WIDTH1 have?  If it was just 5.3 (without any quotes) then your statement becomes something like:

putn(x,5.3)

Which is not valid SAS code because the PUTN() function wants a character value for the second argument (and a numeric value for the first. If you are formatting a character string use the PUTC() function instead.).  In this context the string 5.3 is a number, not a character string.  It might be interpreted as a format specification in locations where such was expected, but that is not what PUTN() expects.

So either add the quotes when referencing the macro variable:

putn(x,"&_width1")

Or make sure the quotes are in the macro variable.

%let _width1="5.3";

So that the resolved SAS code is something like:

putn(x,"5.3")

[Tom]

No need for macro variables.  Just put the formats into another array.

data want ;
  set df1;
  array _invars a b c;
  array _inval[3] $16 ;
  array _formats[3] $8 _temporary_ ('5.1' '5.2' '5.3');
  do i=1 to 3.;
/*I want to use &_width(i) where i change with i in looping setting */
    _inval[i]=putN( _invars[i],_formats[i]);
  end;
run ;