Displaying 1 result from an estimated 1 matches for "list_to_df".
2011 Dec 28
1
Subsetting a data frame vs. subsetting the columns
...ion(x) x[ord]))
# user system elapsed
# 0.022 0.008 0.029
What's going on?
I realise this isn't quite a fair example because the second case
makes a list not a data frame, but I thought it would be quick
operation to turn a list into a data frame if you don't do any
checking:
list_to_df <- function(list) {
n <- length(list[[1]])
structure(list,
class = "data.frame",
row.names = c(NA, -n))
}
system.time(list_to_df(lapply(df, function(x) x[ord])))
# user system elapsed
# 0.031 0.017 0.048
So I guess this is slow because it has to make a copy of...