>>>>> McGehee, Robert writes:
> Hello,
> I wanted to suggest that the below method for split.Date be added to the
> base library to significantly speed up splits with values of class Date.
> In the below example I show a speed improvement of 175x for 1000 data
> points. On a vector of size 1e6, the time difference was 22 minutes for
> split.default versus 0.3 seconds for the split.Date function below (!).
> Note that this improvement will also substantially improve performance
> for the tapply function on class Date as well.
Thanks for the suggestion. Looks good to me, so I've just added this to
r-devel.
Best
-k
> Thanks,
> Robert
> split.Date <- function(x, f, drop=FALSE) {
> x <- split.default(as.integer(x), f, drop=drop)
> for (i in seq(along=x)) class(x[[i]]) <- "Date"
> x
> }
>> vals <- round(1000*rnorm(1e4))
>> date <- rep(Sys.Date() + -1:1, length.out=1e4)
>> system.time(x1 <- split.default(date, vals))
> user system elapsed
> 7.718 0.042 7.761
>> system.time(x2 <- split.Date(date, vals))
> user system elapsed
> 0.044 0.000 0.044
>> all.equal(x1, x2)
> [1] TRUE
> Robert McGehee, CFA
> Geode Capital Management, LLC
> One Post Office Square, 28th Floor | Boston, MA | 02109
> Tel: 617/392-8396 Fax:617/476-6389
> mailto:[EMAIL PROTECTED]
> This e-mail, and any attachments hereto, are intended fo...{{dropped:12}}
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