Hi, I am doing a calculation on a long series using a For Loop. Here is an example of the calculation: accumulate=function(x){ y=0 z=0 for(i in 1:length(x)){ y=y+x[i] z=c(z,y) } return(z[2:length(z)]) }> x=c(1:10) > x[1] 1 2 3 4 5 6 7 8 9 10> accumulate(x)[1] 1 3 6 10 15 21 28 36 45 55>Although the For Loop works, looping through an array is time consuming and inefficient when the series is large. Does anyone know a faster way of doing the same calculation? Thanks! -- Tom [[alternative HTML version deleted]]
tom soyer wrote:> Hi, > > I am doing a calculation on a long series using a For Loop. Here is an > example of the calculation: > > accumulate=function(x){ > y=0 > z=0 > for(i in 1:length(x)){ > y=y+x[i] > z=c(z,y) > > } > return(z[2:length(z)]) > } > > >> x=c(1:10) >> x >> > [1] 1 2 3 4 5 6 7 8 9 10 > >> accumulate(x) >> > [1] 1 3 6 10 15 21 28 36 45 55 > > > Although the For Loop works, looping through an array is time consuming and > inefficient when the series is large. Does anyone know a faster way of doing > the same calculation? Thanks!cumsum(x) is what you want. Duncan Murdoch