[R] Question on memory allocation & loop

[Manoj]

Hello All,
      I am trying to work on writing the following piece of (pseudo)
code in an optimal fashion:

----------------------------------------------------
# Two data frames with some data

a = data.frame(somedata)
b = data.frame(somedata)

for(i in 1:nrow(dt) {
  # Merge dates for a given date into a new data frame
   c = merge(a[a$dt==dt[i],),b[b$dt == dt[i],], by=c(some column));
}
----------------------------------------------------


Now, my understanding is that the data frame c in the above code is
malloc'ed in every count of the loop.  Is that assumption correct?

Is the following attempt a better way of doing things?

----------------------------------------------------
a = data.frame(somedata)
b = data.frame(somedata)

# Pre-allocate data frame c

c = data.frame(for some size);

for(i in 1:nrow(dt) {
  # Merge dates for a given date into a new data frame
   # and copy the result into c

  copy(c, merge(a[a$dt==dt[i],),b[b$dt == dt[i],], by=c(some column));

}
----------------------------------------------------

Now the question is, How can I copy the merged data into my
pre-allocated data frame c ? I tried rbind/cbind but they are pretty
fuzzy about having the right names and dimension hence it fails.

Any help would be greatly appreciated!

Thanks.

Manoj