[R] Reading and coalescing many datafiles.
Peter Dalgaard
p.dalgaard at biostat.ku.dk
Thu Apr 14 18:23:09 CEST 2005
asr at ufl.edu writes:
> Greetings.
>
>
> I've got some analysis problems I'm trying to solve, the raw data for which
> are accumulated in a bunch of time-and-date-based files.
>
> /some/path/2005-01-02-00-00-02
>
> etc.
>
>
> The best 'read all these files' method I've seen in the r-help archives comes
> down to
>
> for (df in my_list_of_filenames )
> {
> dat <- rbind(dat,my_read_function(df))
> }
>
> which, unpleasantly, is O(N^2) w.r.t. the number of files.
>
> I'm fiddling with other idioms to accomplish the same goal. Best I've come up
> with so far, after extensive reference to the mailing list archives, is
>
>
> my_read_function.many<-function(filenames)
> {
> filenames <- filenames[file.exists(filenames)];
> rv <- do.call("rbind", lapply(filenames,my_read_function))
> row.names(rv) = c(1:length(row.names(rv)))
> rv
> }
>
>
> I'd love to have some stupid omission pointed out.
Why? It's pretty much what I would suggest, except for the superfluous
c().
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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