how to combine 60 matrices in R quickly

Question

I have 60 matrices in R named as mat1, mat2....mat60 and I would like to combine them into a big matrix using rbind. I know that I could write something like

Answer 1

I think this question really relates to the OP having to type out the names of the matrices manually. You can use mget to return the matrices in a list and then use do.call and rbind as posed by @Michele like this (assuming the matrices are located in the .GlobalEnv ):

matList <- mget(paste0("mat",1:60),env=globalenv())
bigm <- do.call("rbind" , matList)

Answer 2

I supposed they all have same number of column (and same colnames). If so, try this:

do.call("rbind", matlist)

otherwise:

matlist <- lapply(matlist, as.data.frame)

library(plyr)
rbind.fill(matlist)

EDIT:

adding some timings:

lst <- list()

for(i in 1:1000)
  lst[[i]] <- matrix(rnorm(10000, 100))

f1 <- function()
  do.call("rbind", lst)

f2 <- function(){
  lst <- lapply(lst, as.data.table)
  rbindlist(lst)
}

library(data.table)
library(microbenchmark)

> microbenchmark(f1(), f2())
Unit: milliseconds
 expr       min        lq    median        uq      max neval
 f1()  53.78661  55.22728  63.43546  66.08829 103.1996   100
 f2() 210.46232 215.32043 217.93846 221.35012 333.2758   100

If the OP has got his data in matrices I thought that including lst <- lapply(lst, as.data.table) was the correct way of comparison. Otherwise it would be:

> lst.dt <- lapply(lst, as.data.table)
> f2 <- function(){
+   rbindlist(lst.dt)
+ }
> microbenchmark(f1(), f2())
Unit: milliseconds
 expr      min       lq   median       uq      max neval
 f1() 49.00308 50.28515 54.98947 60.71945 87.66487   100
 f2() 24.23454 28.57692 31.79278 32.75494 63.78825   100

Answer 3

This should be faster:

 library(data.table)
 rbindlist(matList)

EDIT The above solution will work for list of data.frame or list, If you have a list of matrix you should convert them before:

 rbindlist(lapply(ll,as.data.frame))