I'm using R 2.13.1, and I have to calculate the return of a vector of prices. Those prices are an historical price series of a stock. I need to calculate daily gain/loss (%).
Is there a function to calculate it automatically?
Using your sample data, I think you mean the following:
a <- c(10.25, 11.26, 14, 13.56) > diff(a)/a[-length(a)]  0.09853659 0.24333925 -0.03142857
diff returns the vector of lagged differences and
a[-length(a)] drops the last element of a.