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testddply
2009 Nov 19
1
Performance of 'by' and 'ddply' on a large data frame
I've only recently started using R. One of the problems I come up
against is after having extracted a large dataset (>5M rows) out of
database, I realize I need another variable. In this case I have data
frame with dates. I want to find the minimum date for each value of x1
and add that minimum date to my data.frame.
> randomdf <- function(p) {
data.frame(x1=sample(1:10^4, 10^p,