Hi all,

I put some data below, but I have a question about making a varialbe that is it's value minus the value of the last month. I have a variable activemonth_final that is in the format 2020m1, 2020m2, 2020m3, etc. The variable ccda_all_act_ind has a different value for each month. Is there a way I can make a variable that shows ccda_all_act_ind minus it's value from last month? For example, in the 2020m1 case it would show 2020m1-2019m12. Thanks!
Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input float(activemonth_final ccda_all_act_ind)
611    .
647 2206
587    .
671 2486
659 2241
623    .
719 3084
695 2970
599    .
707 3079
683 2793
635    .
684 2875
708 3209
672 2517
612    .
588    .
720 3213
660 2230
624    .
636 2077
696 3160
600    .
648 2178
697 3160
721 3200
649 2196
685 2816
613    .
589    .
709 3147
661 2213
625    .
637 2047
673 2658
601    .
710 3178
638 2182
650 2297
686 2980
698 3226
602    .
674 2746
626    .
614    .
494    .
662 2250
590    .
722 3195
615    .
663 2231
627    .
603    .
699 3198
639 2299
579    .
723 2941
675 2637
711 3182
591    .
651 2256
687 2917
712 3172
652 2230
676 2743
700 3215
616    .
724 2973
628    .
688 2990
604    .
640 2295
592    .
664 2227
677 2699
701 3126
689 3067
629    .
593    .
725 3051
617    .
641 2231
653 2194
713 3051
665 2299
605    .
642 2276
678 2672
594    .
654 2231
702 3076
630    .
606    .
666 2349
726 2983
690 2981
714 3180
582    .
618    .
703 3147
end
format %tm activemonth_final
------------------ copy up to and including the previous line ------------------

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