[R] Thoughts for faster indexing

Jim Holtman jholtman at gmail.com
Thu Nov 21 12:34:12 CET 2013

you need to show the statement in context with the rest of the script.  you need to tell us what you want to do, not how you want to do it.  

Sent from my iPad

On Nov 20, 2013, at 15:16, Noah Silverman <noahsilverman at g.ucla.edu> wrote:

> Hello,
> I have a fairly large data.frame.  (About 150,000 rows of 100
> variables.) There are case IDs, and multiple entries for each ID, with a
> date stamp.  (i.e. records of peoples activity.)
> I need to iterate over each person (record ID) in the data set, and then
> process their data for each date.  The processing part is fast, the date
> part is fast.  Locating the records is slow.  I've even tried using
> data.table, with ID set as the index, and it is still slow.
> The line with the slow process (According to Rprof) is:
> j <- which( d$id == person )
> (I then process all the records indexed by j, which seems fast enough.)
> where d is my data.frame or data.table
> I thought that using the data.table indexing would speed things up, but
> not in this case.
> Any ideas on how to speed this up?
> Thanks!
> -- 
> Noah Silverman, M.S., C.Phil
> UCLA Department of Statistics
> 8117 Math Sciences Building
> Los Angeles, CA 90095
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