topic Re: Dynamic Do Loop in SAS Programming

Dynamic Do Loop

arpitsharma27 — Thu, 22 Mar 2018 14:34:30 GMT

Team,

I have the following code:

%let char_var_cnt=12;
%let sixpack=6;
%let quotient=%eval(&char_var_cnt./&sixpack.);
%let remainder=%sysfunc(mod(&char_var_cnt.,&sixpack.));
%put quotient=&quotient.;
%put remainder=&remainder.;

%macro looping;
	%do i=1 %to &sixpack.;
		%do k=1 %to &char_var_cnt.;
			%let k&i._&k.=var&k.;
			%put list is k&i._&k.;
		%end;
	%end;
%mend;

%looping;

The above code creates macro variable

list is k1_1
list is k1_2
list is k1_3
list is k1_4
list is k1_5
list is k1_6
list is k1_7
list is k1_8
list is k1_9
list is k1_10
list is k1_11
list is k1_12
list is k2_1
list is k2_2
list is k2_3

list is k2_4
list is k2_5
list is k2_6
list is k2_7

What I actually want is:

It creates the following macro variable

k1_1 K1_2

k2_3 K2_4

k3_1 K3_6

k4_1 K4_8

k5_9 K5_10

k6_11 K6_12

Each of these K1_1, k1_2, k2_3 etc macro variables need to take value from another macro var&i.

The char_var_cnt macro variable is dynamic.

The sixpack macro variable is static.

To summarize:

If char_var_cnt is equal to 12 then i want the following macro parameters:

k1_1 K1_2

k2_3 K2_4

k3_1 K3_6

k4_1 K4_8

k5_9 K5_10

k6_11 K6_12

If char_var_cnt is equal to 24 then i want the following macro parameters:

k1_1 K1_2 k1_3 K1_4
k2_5 K2_6 k2_7 K2_8
k3_9 K3_10 k3_11 K3_12
k4_13 K4_14 k4_15 K4_16
k5_17 K5_18 k5_19 K5_20
k6_21 K6_22 k6_23 K6_24

Can you please help me with it?

Re: Dynamic Do Loop

ballardw — Thu, 22 Mar 2018 15:09:27 GMT

You have created the macro variables, at least temporarily, but you didn't examine the values properly. Please see:

%macro looping;
	%do i=1 %to &sixpack.;
		%do k=1 %to &char_var_cnt.;
			%let k&i._&k.=var&k.;
			%put list k&i._&k. is &&k&i._&k.;
		%end;
	%end;
%mend;

I do not have any of your var&k variables to examine but to get the value of them you could use

%macro looping;
	%do i=1 %to &sixpack.;
		%do k=1 %to &char_var_cnt.;
			%let k&i._&k.= &&var&k.;
			%put list k&i._&k. is &&k&i._&k.;
		%end;
	%end;
%mend;

If you want the variables to exist outside of your macro looping you will have do something something additional such as add a %global statement as each is created. Otherwise the only exist inside your loop macro.

You can use %put with key words to generate lists of macro variables and their values without having to %put each one.

See:

%macro looping;
	%do i=1 %to &sixpack.;
		%do k=1 %to &char_var_cnt.;
			%let k&i._&k.= var&k.;
			
		%end;
	%end;
   %put _local_;
%mend;

Re: Dynamic Do Loop

arpitsharma27 — Thu, 22 Mar 2018 15:17:56 GMT

Here is the revised code:

I have provided a snippet of log.

The ones that i DONT want are highlighted RED.

The ones that I WANT are highlighted GREEN.

%macro alpha(start=,stop=);

	%do z=&start. %to &stop.;
	%global var&z.;
		%let var&z.=alpha&z.;
	%end;
%mend;
%alpha(start=1,stop=12);

%let char_var_cnt=12;
%let sixpack=6;
%let quotient=%eval(&char_var_cnt./&sixpack.);
%let remainder=%sysfunc(mod(&char_var_cnt.,&sixpack.));
%put quotient=&quotient.;
%put remainder=&remainder.;

%macro looping;
	%do i=1 %to &sixpack.;
		%do k=1 %to &char_var_cnt.;
			%let k&i._&k.=&&var&k.;
			%put list is k&i._&k. &&k&i._&k.;
		%end;
	%end;
%mend;

%looping;

I get this in log:

list is k1_1 alpha1
list is k1_2 alpha2
list is k1_3 alpha3
list is k1_4 alpha4
list is k1_5 alpha5

list is k1_6 alpha6
list is k1_7 alpha7
list is k1_8 alpha8
list is k1_9 alpha9
list is k1_10 alpha10
list is k1_11 alpha11
list is k1_12 alpha12
list is k2_1 alpha1
list is k2_2 alpha2
list is k2_3 alpha3
list is k2_4 alpha4
list is k2_5 alpha5

list is k2_6 alpha6
list is k2_7 alpha7
list is k2_8 alpha8
list is k2_9 alpha9

......

Re: Dynamic Do Loop

Tom — Thu, 22 Mar 2018 17:34:03 GMT

@arpitsharma27 wrote:

Here is the revised code:

I have provided a snippet of log.

The ones that i DONT want are highlighted RED.

The ones that I WANT are highlighted GREEN.
 
......

What is the LOGIC for deciding which once to create? Can you describe it in words?

I don't see the pattern in this list.

list is k1_1 alpha1
list is k1_2 alpha2
list is k2_3 alpha3
list is k2_4 alpha4

Are you just setting K equal to CEIL(ALPHA/2)?

Try getting the looping logic right in a data step where it is easier to debug and then translating to macro logic. or just use CALL SYMPUTX() to generate the macro variables in the data step.

Re: Dynamic Do Loop

Tom — Thu, 22 Mar 2018 20:00:53 GMT

Coding is much easier in data steps. Plus the DO loop is much more powerful than the %DO loop.

Not sure what you want to do but I can generate your pattern of K and ALPHA values using data steps like this.

I added extra DO loops so you can play with settings of two input numbers and see how it works.

data _null_;
  do sixpack=6;
    do char_var_cnt=12,24,17 ;
      put / sixpack= char_var_cnt= / 12*'-' ;
      alpha=1 ;
      do k=1 by 1 while (alpha <= char_var_cnt) ;
        put k= @;
        do i=1 to ceil(char_var_cnt/sixpack) while (alpha <= char_var_cnt);
         put alpha= @;
         alpha+1;
        end;
        put;
      end;
    end;
  end;
run;

sixpack=6 char_var_cnt=12
------------
k=1 alpha=1 alpha=2
k=2 alpha=3 alpha=4
k=3 alpha=5 alpha=6
k=4 alpha=7 alpha=8
k=5 alpha=9 alpha=10
k=6 alpha=11 alpha=12

sixpack=6 char_var_cnt=24
------------
k=1 alpha=1 alpha=2 alpha=3 alpha=4
k=2 alpha=5 alpha=6 alpha=7 alpha=8
k=3 alpha=9 alpha=10 alpha=11 alpha=12
k=4 alpha=13 alpha=14 alpha=15 alpha=16
k=5 alpha=17 alpha=18 alpha=19 alpha=20
k=6 alpha=21 alpha=22 alpha=23 alpha=24

sixpack=6 char_var_cnt=17
------------
k=1 alpha=1 alpha=2 alpha=3
k=2 alpha=4 alpha=5 alpha=6
k=3 alpha=7 alpha=8 alpha=9
k=4 alpha=10 alpha=11 alpha=12
k=5 alpha=13 alpha=14 alpha=15
k=6 alpha=16 alpha=17