Re: [R] efficient way to do 2-level loops

On Thu, Sep 06, 2012 at 10:50:00AM -0400, Jie wrote: > Dear All, > > Suppose I have two loops and would like to convert it to sapply, how > to achive the goal? > Below is an example, the calculation inside the loop is not essential, > so please do not use tricks for this part. > a <- 1:5 > b <- 1:

Re: [R] efficient way to do 2-level loops

Hello, Use expand.grid. One line at a time, to make it clearer: a <- 1:5 b <- 1:10 m <- expand.grid(b, a)[, c(2, 1)] resu <- matrix(NA, nrow=5, ncol=10) for (i in 1:5) { for (j in 1:10) # --> was 1:5 in your post { resu[i,j]=a[i]+b[j] # will be more complicated } }