Subtract month from YYYYMM macro variable

[somepathak]

Hi All, 

I am new to SAS and need help with subtracting months from a macro variable storing date in YYYYMM format. I tried the following code but it isn't working, any help on this would be appreciated. 

The desired value for last_mon is 201909

%let score_month = 201910; /*YYYYMM format */
%let mon_var = %sysfunc(inputn(putn(&score_month,6.)!!'01',yymmdd8.)); /*converting to sas date format by adding day as 01 */
%let last_mon = %sysfunc(intnx(month,&mon_var,-1),yymmn6.); /*subtracting 1 month */ 
%put &score_month***&last_mon***

Notes :

1 OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

72

73 %let score_month = 201910; /*YYYYMM format */

74 %let mon_var = %sysfunc(inputn(putn(&score_month,6.)!!'01',yymmdd8.)); /*converting to sas date format by adding day as

74 ! 01 */

WARNING: Argument 1 to function INPUTN referenced by the %SYSFUNC or %QSYSFUNC macro function is out of range.

NOTE: Mathematical operations could not be performed during %SYSFUNC function execution. The result of the operations have been set

to a missing value.

75 %let last_mon = %sysfunc(intnx(month,&mon_var,-1),yymmn6.); /*subtracting 1 month */

76 %put &score_month***&last_mon***;

201910***.***

77

78 OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

90

[PaigeMiller · Accepted solution]

Maxim 28 ... do not format macro variables for the purpose of performing arithmetic or logical operations.

%let score_month = 201910; 
%let mon_var = %sysfunc(inputn(&score_month,yymmn6.)); /* Not formatted */
%let last_mon = %sysfunc(intnx(month,&mon_var,-1)); /* Not formatted */
%put &=score_month &=last_mon;

Now to see what the integer in &last_mon represents, so humans can understand it, formatting is appropriate.

%put %sysfunc(putn(&last_mon,yymmn6.));