[R-sig-DB] How to store R objects in blob in MySQL?

[Rainer M Krug]

On 08/02/2008, Dirk Eddelbuettel <edd using debian.org> wrote:
>
>
> 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:


Ooops - I must have overlooked that email - sorry.

But this definitely answers my question. Thanks a lot,

Rainer


   From: Dirk Eddelbuettel <edd using eddelbuettel.com>
>    To: Rainer M Krug <r.m.krug using gmail.com>
>    Cc: Richard Pearson <richard.pearson using postgrad.manchester.ac.uk>,
>         R-help using 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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> |
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>
> --
> Three out of two people have difficulties with fractions.
>



-- 

-- 
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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