topic Re: Incremental change to a value of macro variable in SAS Programming

Incremental change to a value of macro variable

Lida — Mon, 16 Jul 2018 17:18:00 GMT

Hello,

I am trying to change a value for a macro variable decreasing it by 0.01 with each iteration and I cannot understand why this does not work. Could anyone tell me what is wrong in my code? Thank you!

%macro Low_cost_diet (K_cost_m=,
b=);

%do i=1 %to &b.;

%OptDietPattern (
DRIAG=16
,DRI=2
,DRIAG_Label='M - 2 TO 3 YRS'
,outputdata=OptimalDiet /*output data set*/
,Round=r15
,k_SOD=1
,k_IRON=1
,k_VitD=1
,k_CAL=1
,k_FI=1
,k_COST=&k_COST_m.
);

%let k_COST=%eval(&k_COST-0.01);

%end;

%mend;

%Low_cost_diet (K_cost_m=1,b=2);

Re: Incremental change to a value of macro variable

PaigeMiller — Mon, 16 Jul 2018 17:19:39 GMT

%eval only performs integer arithmetic. You are trying to perform non-integer arithmetic using %eval.

You could use %sysevalf which will perform non-integer arithmetic.

Re: Incremental change to a value of macro variable

Tom — Mon, 16 Jul 2018 17:20:27 GMT

%EVAL() does not do floating point math.

Either use %SYSEVALF() or parameterize the macro differently so that you are passing in an integer instead of a floating point value. Note it is very had to represent a floating point value exactly as a text string.

Re: Incremental change to a value of macro variable

Lida — Mon, 16 Jul 2018 17:26:53 GMT

thank you but it still does not work..

WARNING: Apparent symbolic reference K_COST not resolved.

ERROR: A character operand was found in the %EVAL function or %IF condition where a numeric operand is required. The condition was:

&k_COST-0.01

ERROR: The macro LOW_COST_DIET will stop executing.

Re: Incremental change to a value of macro variable

Tom — Mon, 16 Jul 2018 17:28:21 GMT

Are you calling the macro variable K_COST or K_COST_M?

Re: Incremental change to a value of macro variable

ballardw — Mon, 16 Jul 2018 17:29:36 GMT

I suspect in the long run you might want to consider making your macro variable integer and then doing a conversion in the step using

,k_COST=&k_COST_m.

Or not incrementing the macro variable at all and using something like

,k_COST=&k_COST_m - (0.01 * (&i - 1) )

Re: Incremental change to a value of macro variable

Lida — Mon, 16 Jul 2018 17:33:05 GMT

I want to run %OptDietPattern macro starting with k_COST=1 and in the next iteration of that macro I want to decrease the cost by 0.01. I will add the data step for each iteration later ..now I just need to make reduction in cost work for each iteration.

Re: Incremental change to a value of macro variable

Astounding — Mon, 16 Jul 2018 17:44:01 GMT

The message is correct. Your exterior macro %LOW_COST_DIET does not contain a macro variable named &K_COST. Only the interior macro (%OptDietPattern) contains &K_COST.

I suspect you want to change this statement:

%let k_COST=%eval(&k_COST-0.01);

Instead, use:

%let k_COST_m = %sysevalf (&k_COST_m - 0.01);

Re: Incremental change to a value of macro variable

Lida — Mon, 16 Jul 2018 17:48:22 GMT

Hurray.. it works… Thank you a lot Astounding! Much appreciated! I spent the whole morning trying to make it work...You saved me another half of the day!

Thank you very much!