Re: [R] hex format

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Sat 09 Apr 2005 - 02:53:03 EST

Earl F. Glynn wrote:

>I recently discovered R's writeBin and readBin functions. readBin, in
>particular, looks like an extremely powerful tool for loading external
>files. This might be an easier way to perform some one-time data
>manipulations instead of writing a separate C, Perl or Delphi program to
>manipulate data before bringing it into R for analysis.
>
>readBin returns a "raw" data type that looks like an array of bytes that R
>displays in hex. That's where my problem begins and why I joined this "hex
>format" thread.
>
>
That's only one possibility. readBin can return a number of different types.

>I'd love to manipulate this raw hex data, but R makes using these hex bytes
>quite difficult to use (or more difficult than I think it should be based on
>how easy it is in other languages). I might want to interpret a byte, or a
>string of bytes, as characters.
>
A simple solution to this would be to implement a "raw connection", that takes a raw variable and lets you read it using readBin.

> Or, I might want to interpret pairs of
>bytes as 2-byte unsigned (or possibly signed) integers. Or, I might want to
>interpret 3-bytes at a time as RGB values (in either RGB or BGR order). Or,
>I might want to interpret 8-bytes at a type as a IEEE754 floating point
>number.
>
>Every time someone wants to manipulate this raw data in R, as far as I can
>tell now, one must start from scratch and do all sorts of manipulations on
>these hex byte values to get characters, or integers, or doubles. And
>because it's not that easy (but it's not that hard either, more of an
>annoyance), I guess many just go back to C to get that job done there and
>then return to R.
>
>
Currently you can do it by writing the raw data out to a temporary file and reading it back in. It would be nice to allow this to happen without the temporary file.

Duncan Murdoch



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