Faster way of binding multiple rows of data than rbind?
Ken Termiso wrote:
Hi all,
I have a vector that contains the row numbers of data taken from several
filtering operations performed on a large data frame (20,000rows x
500cols).
In order to output this subset of data, I've been looping through the
vector containing the row numbers (keepRows).
output <- data.frame(row.names = rownames(bigMatrix))
for(i in keepRows)
{
output <- rbind(output, bigMatrix[i, ])
}
As you may guess, doing all of these rbinds takes a LOT of time, so I'm
wondering if there's a workaround where I can maybe use an intermediate
matrix-like object to store the loop output, and then coerce it back to
a data frame after the loop is complete??
The indexing operations in R are very flexible. You can do this in a single operation as output <- bigMatrix[keepRows, ]