[R] Help with speed (replacing the loop?)

[Dimitri Liakhovitski]

Thanks a lot, Steve!
match sounds very promising - that means I only need a loop across predictors.

As far as "get more memory" advice is concerned: I already have "more" memory :)

On Wed, Jan 11, 2012 at 11:14 AM, Steve Lianoglou
<mailinglist.honeypot at gmail.com> wrote:
> Hi,
>
> On Wed, Jan 11, 2012 at 10:50 AM, Dimitri Liakhovitski
> <dimitri.liakhovitski at gmail.com> wrote:
>> Thanks a lot, Steve. I have one question (below):
>>
>>
>>> ====
>>> library(data.table)
>>>
>>> ## your data
>>> xx <- data.table(group=c(rep("group1",5),rep("group2",5)),
>>>                 a=1:10, b=seq(10,100,by=10), key="group")
>>> yy <- data.table(group=c("group1","group2"), a=c(10,20), b=c(2,3),
>>>                 key="group")
>>>
>>> ## temp data.table to get your ducks in a row
>>> m <- merge(xx, yy, by="group", suffixes=c(".x", ".y"))
>>
>>
>> Dimitri: The step above (merge) - I was thinking of it but decided
>> against it because my xx already fills up tons of memory. When I merge
>> xx and yy that doubles the number of variables - I am afraid my memory
>> won't hold that much stuff...
>
> Fair enough ... how about just using `match`, then, ie:
>
> R> aa <- x$a * y$a[match(x$group, y$group)]
>
> Should do the trick, no?
>
> -steve
>
> --
> Steve Lianoglou
> Graduate Student: Computational Systems Biology
>  | Memorial Sloan-Kettering Cancer Center
>  | Weill Medical College of Cornell University
> Contact Info: http://cbio.mskcc.org/~lianos/contact



-- 
Dimitri Liakhovitski
marketfusionanalytics.com