How to apply a function to every consecutive n elements in a vector

Question

I am trying to convert quarterly returns to yearly returns. Given a vector of quarterly returns, how can this be done?

I am fairly new to R-programming, so I haven\'t r

Answer 1

An option:

    c(by(a, rep(1:(length(a)/4), each = 4), FUN = function(x) 

  (1 + x[1]) * (1 + x[2]) * (1 + x[3]) * (1 + x[4])-1

  )
))

        1         2 
0.2578742 0.1800339