How to store R objects in blob in MySQL?

On 8 February 2008 at 14:31, Rainer M Krug wrote:
| Hi
|
| I was thinking - how can I store R objects in a blob field? Normal
| dataframes can be nicely stored in a table - but is theree a mechanism
to
| store objects in a blob field?

I tried to answer that question in an email I sent you two days ago:

   To: Rainer M Krug <r.m.krug at gmail.com>
   Cc: Richard Pearson <richard.pearson at postgrad.manchester.ac.uk>,
        R-help at r-project.org
   Subject: Re: [R] advice requested re: building "good" system (R, SQL
db)
        for handling large datasets
   Date: Wed, 6 Feb 2008 09:58:56 -0600

   On Wed, Feb 06, 2008 at 02:34:52PM +0200, Rainer M Krug wrote:

   > R objects in blobs - I never thought about that. Could you elaborate

on how

   > to do something like that (I am using RMySQL)?

   Look at help(serialize) -- any R object can be turned into a suitable
   representation, either binary (more efficient) or ascii (possibly
   'safer').

   Store that, retrieve it later, reconstruct the object and be merry :)

   > tmpDf <- data.frame(a=1:10, b=LETTERS[1:10], c=rnorm(10))
   > serDf <- serialize(tmpDf, NULL, ascii=TRUE)
   > rm(tmpDf)
   > head(unserialize(serDf))

     a b          c
     1 1 A -0.6945820
     2 2 B -0.2960084
     3 3 C -0.2514302
     4 4 D -0.7318635
     5 5 E -0.1698489
     6 6 F  0.4331521

     >

   Dirk

Now, look at what serDf actually is -- an ascii vector.  You can simply
write
that to virtually any db system into a char field of variable length.  You
could also create an actual blob object via
        serDfBin <- serialize(tmpDf, NULL, ascii=FALSE)
but you can't print that easily to the console for checks pp.  It is
however
a binary blob, so if you wanted to write that, you could.

Does this help?

Dirk


| I am using MySQL under Linux.
|
| Thanks
|
| Rainer
|
|
| --
| Rainer M. Krug, Dipl. Phys. (Germany), MSc Conservation Biology (UCT)
|
| Plant Conservation Unit Department of Botany
| University of Cape Town
| Rondebosch 7701
| South Africa
|
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