cumulative returns

[okyk_86]

dear sas members

hi

i'm trying to calculate cumulative returns, but i dont know how can i do... 

i want to calculate monthly return by using daily returns.

[(1+R1)(1+R2)...(1+Rn)]-1

my data set:

date return(%)

19910801 5

19910802 3

19910803 2

19910804 3

...

19910831 3

19910901 -1

19910902 -0.8

...

(from 1991081 to 20151231)

Is there any way to calculate cumulative return for each month?

Your help is truly appreciated!

Thanks,

[RW9]

Hi,

Generally a good idea to search for things first, I have seen at least three similar posts in the last day or two:

https://communities.sas.com/t5/forums/searchpage/tab/message?q=cumulative

[mkeintz · Accepted solution]

Instead of keeping running products, sum the logs of (1+returnpct/100).  At the end of the month take the antilog and subtract 1 (and mult by 100 if you want percentages).

In SAS, you can merge a dataset with itself, but offset by one record (see "firstobs=2") to determine whether the record in hand is the last for the current month:

data mreturns (drop=sumlog);
  merge dreturns  dreturns(firstobs=2 keep=date rename=(date=nxtdate));
  retain sumlog 0;
  sumlog=sum(sumlog,log10(1+returnpct/100));
  if month(date)^=month(nxtdate) then do;
    mreturn=10**sumlog-1;
    output;
    sumlog=0;
  end;
run;

[okyk_86]

i'm not good at mathmatics... so i can't exactly understand about the steps....

I solved it.

Thank you so much!