Hi,   I am trying to compute the Relative Strengh Index (RSI) of 500 stocks but on a monthly basis. I wrote the following code based on a paper found online, however, there are some mistakes but I do not know how to fix them. Moreover, there are some statements that I do not understand what "%do i=16 %to 7570;" stand for in the code.   data Project.MonthlyPrice;     set RSI;     by PERMNO;     lprc = lag(prc);     if prc>lprc then gain = prc-lprc;     if prc<lprc then loss = lprc-prc;     if first.PERMNO then do;   gain = .;   loss = .;     end;     retain months 0;     months+1;     if first.PERMNO then months = 1;     if gain = . then gain = 0;     if loss = . then loss = 0;     retain sumgain 0;     sumgain = sumgain + gain;     retain sumloss 0;     sumloss = sumloss + loss;     if months=15 then do;         AveGain = (sumgain-gain) / 14;  AveLoss = (sumloss-loss) / 14;    RS =  AveGain / AveLoss;  RSI = 100-100/(1+RS);     end;     drop sumgain sumloss; run; %macro calRSI();     %do i=16 %to 7570;         data Project.MonthlyPrice;      set RSI;      lAveGain = lag1(AveGain);      lAveLoss = lag1(AveLoss);      if months = &i then do;          AveGain = (lAveGain*13+gain)/14;   AveLoss = (lAveLoss*13+loss)/14;   RS =  AveGain / AveLoss;   RSI = 100-100/(1+RS);      end;     %end; %mend; data Project.MonthlyPrice;     set RSI; run;     Thank in advance ... View more