How to clean up R memory (without the need to restart my PC)?

Question

I am running my code in R (under Windows) which involves a lot of in-memory data. I tried to use rm(list=ls()) to clean up memory, but seems the memory is still

Answer 1

memory.size(max=T) # gives the amount of memory obtained by the OS
[1] 1800
memory.size(max=F) # gives the amount of memory being used
[1] 261.17

Using Paul's example,

m = matrix(runif(10e7), 10000, 1000)

Now

memory.size(max=F)
[1] 1024.18

To clear up the memory

gc()
memory.size(max=F)
[1] 184.86

In other words, the memory should now be clear again. If you loop a code, it is a good idea to add a gc() as the last line of your loop, so that the memory is cleared up before starting the next iteration.