Hello,   I am having a lot of trouble creating several dummy-variables with two loops, and I have no idea how to do it.   The goal is to make dummy-variables from categorical variables recorded at specific times.   As of now (for 5 years with 5 categories), to do it manually it would be like: data tmp; set data1;   if y_1=0 then cat0_time_0=1; else cat0_time_0=0; if y_2=0 then cat0_time_1=1; else cat0_time_1=0; if y_3=0 then cat0_time_2=1; else cat0_time_2=0; if y_4=0 then cat0_time_3=1; else cat0_time_3=0; if y_5=0 then cat0_time_4=1; else cat0_time_4=0; if y_1=1 then cat1_time_0=1; else cat1_time_0=0; if y_2=1 then cat1_time_1=1; else cat1_time_1=0; if y_3=1 then cat1_time_2=1; else cat1_time_2=0; if y_4=1 then cat1_time_3=1; else cat1_time_3=0; if y_5=1 then cat1_time_4=1; else cat1_time_4=0; if y_1=2 then cat2_time_0=1; else cat2_time_0=0; if y_2=2 then cat2_time_1=1; else cat2_time_1=0; if y_3=2 then cat2_time_2=1; else cat2_time_2=0; if y_4=2 then cat2_time_3=1; else cat2_time_3=0; if y_5=2 then cat2_time_4=1; else cat2_time_4=0; if y_1=3 then cat3_time_0=1; else cat3_time_0=0; if y_2=3 then cat3_time_1=1; else cat3_time_1=0; if y_3=3 then cat3_time_2=1; else cat3_time_2=0; if y_4=3 then cat3_time_3=1; else cat3_time_3=0; if y_5=3 then cat3_time_4=1; else cat3_time_4=0; if y_1=4 then cat4_time_0=1; else cat4_time_0=0; if y_2=4 then cat4_time_1=1; else cat4_time_1=0; if y_3=4 then cat4_time_2=1; else cat4_time_2=0; if y_4=4 then cat4_time_3=1; else cat4_time_3=0; if y_5=4 then cat4_time_4=1; else cat4_time_4=0; run;   y_3=4 means "Year 3 for category 4" and so on.   But I need to have it more macro-based, so that one only need to specify the maximum amount of categories and years. However, I just can't get it to work.   The "closest" I have gotten is through this attempt:   %MACRO time_categorical_to_binary(time_max=, number_cat=);   data tmp; set data1; %DO i = 0 %to &time_max; %DO j = 0 %to &number_cat; if y_&i.=1 then cat_&j._time_&i.=1; else cat_&j._time_&i.=0;  run; %END; %END; %MEND time_categorical_to_binary;   %time_categorical_to_binary(time_max=4, number_cat=5);   But it seems like SAS doesn't like it when trying to create two indicators to the same variable.   Does anyone have any ideas how to make this doable? I use SAS 9.4 ... View more