Re: [R] Importing binary data

[Uwe Ligges]

Uli Tuerk wrote:
Hi everybody!
I've a large dataset, about 2 Mio entries of the format which I would like 
to import into a frame:
<integer><integer><float><string><float><string><string>

Because to the huge data amount I've choosen a binary format instead 
of a text format when exporting from Matlab.
My import function is attached below. It works fine for only some entries 
but is deadly slow when trying to read the complete set. 

Does anybody has some pointers for me for improving the import or handling 
such large data sets? 
Suggestion:
a) Use a database!!!

And only for very strong reasons against a):
b) Rewrite your import code in C.
c) optimize the code below by initializing the objects in full length 
(e.g. imp.v <- numeric(n)) (maybe you can read it from the header or 
derive the size from the size of the file  ....)

Uwe Ligges

Thanks in advance!
Uli

read.DET.data <- function ( f ) {
        counter <- 1
        spk.v <- c()
        imp.v <- c()
        score.v <- c()
        th.v <- c()
        ses.v <- c()
        rec.v <- c()
        type.v <- c()
        fid <- file( f ,"rb")
        tempi <- readBin(fid , integer(), size=1, signed=FALSE)
        while ( length(tempi) != 0) {
                spk.v[ counter ] <- tempi
                imp.v[ counter ] <- readBin(fid, integer(), size=1, signed=FALSE)
                score.v[ counter  ] <- readBin(fid, numeric(), size=4)
                type.v[ counter ] <- readBin(fid, character())
                th.v[ counter ] <- readBin(fid, numeric(), size=4)
                ses.v[ counter ] <- readBin(fid, character())
                rec.v[ counter ] <- readBin(fid, character())
                counter <- counter + 1
                tempi <- readBin(fid, integer(), size=1, signed=FALSE)
        }
        close( fid )
        spkf <- factor ( spk.v )
        impf <- factor ( imp.v )
        
        det.f <- data.frame( spk=spkf, imp=impf, score=score.v, th=th.v, ses=ses.v, 
rec=rec.v, type=type.v)
        det.f
}
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