Avoid copying the whole vector when replacing an element (a[1] <- 2)

Question

When replacing an element in a vector such as

a <- 1:1000000
a[1] <- 2

R copies the whole vector, replaces the element in the new vec

Answer 1

You can do this with the ff package which is on CRAN. Using ff, your data is stored on disk and indexing will only affect that specific element you are indexing

require(ff)
a <- ff(1:1000000)
a[1] <- 2

For info. These are timings, so it is a lot faster for your toy case.

require(ff)
a <- 1:100000000
b <- ff(a)
system.time(a[1] <- 2)
 user  system elapsed 
0.440   0.592   1.056 
system.time(b[1] <- 2)
 user  system elapsed 
0.004   0.000   0.001