I think you want
output <- do.call(rbind,lapply(z,matrix,ncol=10,byrow=TRUE))
i.e. combining @BlueMagister's use of do.call(rbind,...) with an lapply statement to convert the individual list elements into 11*10 matrices ...
Benchmarks (showing @flodel's unlist solution is 5x faster than mine, and 230x faster than the original approach ...)
n <- 1000
z <- replicate(n,matrix(1:110,ncol=10,byrow=TRUE),simplify=FALSE)
library(rbenchmark)
origfn <- function(z) {
output <- NULL
for(i in 1:length(z))
output<- rbind(output,matrix(z[[i]],ncol=10,byrow=TRUE))
}
rbindfn <- function(z) do.call(rbind,lapply(z,matrix,ncol=10,byrow=TRUE))
unlistfn <- function(z) matrix(unlist(z), ncol = 10, byrow = TRUE)
## test replications elapsed relative user.self sys.self
## 1 origfn(z) 100 36.467 230.804 34.834 1.540
## 2 rbindfn(z) 100 0.713 4.513 0.708 0.012
## 3 unlistfn(z) 100 0.158 1.000 0.144 0.008
If this scales appropriately (i.e. you don't run into memory problems), the full problem would take about 130*0.2 seconds = 26 seconds on a comparable machine (I did this on a 2-year-old MacBook Pro).