[R] Questions about readBin function (Was: dec2bin?)

[Roger D. Peng]

I think you can use 'seek()' here, but it may not be completely reliable on all 
platforms.

-roger

Tuszynski, Jaroslaw W. wrote:
> Hi,
> 
> The latest version of R had some changes to functions "readbin() and
> writeBin() [which] now support raw vectors as well as filenames and
> connections.". As a result I am working on retiring "raw2bin" and "bin2raw"
> functions from "caTools" package which do exactly the same. Thanks to Prof.
> Ripley for bringing this change to my attention.
> 
> Which brings me to my question: how to use readBin function to read the
> whole file or vector "con" and not just requested number of elements (n)
> from it? In other words what to do if I do not know what to set argument "n"
> to ("The (maximal) number of records to be read"), and want to read all
> records?  
> 
> So far the simplest solution I found is to measure vector length (or file
> size) of "con" and set n to length()%/%size. Which gets quite messy if
> "size" is not provided and have to be deduced from "what" (see code below).
> Am I missing something? Is there an easier way to read the whole file or
> vector? Shouldn't that be the default?
> 
> readBin(con, what, n = 1, size = NA, signed = TRUE, endian =
> .Platform$endian)
> 
> bin2raw = function(x, ...) writeBin(x, raw(), ...) # old bin2raw can be
> easily written using curent writeBin
> 
> raw2bin = function(r, what, size=NA, ...)
> {
>   TypeList = c("logical", "integer", "double", "complex", "character",
> "raw", 
>                "numeric", "int")
>   if (!is.character(what) || length(what) != 1 || !(what %in% TypeList)) 
>     what <- typeof(what)
>   if (!is.vector(r) || mode(r) == "list") 
>     stop("raw2bin: 'r' has to be vector of type 'raw'")
>   if (what=="raw") return(r)
>   if (!is.na(size)) nBits=size 
>   else nBits = switch(match(typeof(x), TypeList), 4, 4, 8, 16, 2, 1, 8, 4) 
>   n = length(r)
>   if (n%%nBits) 
>     stop("raw2bin: number of elements in 'r' is not multiple of 'size'")
>   x = readBin(r, what, n = n%/%nBits, size=size, ...)
>   return (x)
> }
> 
>  Jarek 
> ====================================================\==== 
>  Jarek Tuszynski, PhD.                           o / \ 
>  Science Applications International Corporation  <\__,|  
>  (703) 676-4192                                   ">  \ 
>  Jaroslaw.W.Tuszynski at saic.com                     `   \
> 
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-- 
Roger D. Peng
http://www.biostat.jhsph.edu/~rpeng/