R help - Aug 2007 - Connecting to database on statup

Hello,
Q/ Is it possible to create a DBMS connection automatically on startup of R?
(Making sure of course that the db server has been started...)
I am running MySQL on Mac OS X 10.4.2 with R2.4.1.

I have tried to write a function using the RMySQL commands (below) and place
them in .First of .RProfile:

drv <- dbDriver("MySQL")
dbcon <- dbConnect(drv, {other parameters present in my.cnf file}
dbname="mydbName")

DOES create a connection when entered into my R console individually but NOT
when I place them in a function, i.e.,

condb <- function() {
	drv <- dbDriver("MySQL")
	dbcon <- dbConnect(drv, dbname="mydbName")
	dbGetInfo(db)
	}

When the function is called, the dbGetInfo(dbcon) does return connection info
but no connection object is present.

I would be ver grateful for any guidance on where I have gone wrong. Thank you.

Mark Ruddy
PhD student
Geography Dept., Royal Holloway (University of London)
Egham, UK.


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On Sat, 11 Aug 2007, Ruddy M wrote:
> Hello,
> Q/ Is it possible to create a DBMS connection automatically on startup of
R? (Making sure of course that the db server has been started...)
> I am running MySQL on Mac OS X 10.4.2 with R2.4.1.
>
> I have tried to write a function using the RMySQL commands (below) and
place them in .First of .RProfile:
>
> drv <- dbDriver("MySQL")
> dbcon <- dbConnect(drv, {other parameters present in my.cnf file}
dbname="mydbName")
>
> DOES create a connection when entered into my R console individually but
NOT when I place them in a function, i.e.,
>
> condb <- function() {
> 	drv <- dbDriver("MySQL")
> 	dbcon <- dbConnect(drv, dbname="mydbName")
> 	dbGetInfo(db)
> 	}
>
> When the function is called, the dbGetInfo(dbcon) does return connection 
> info but no connection object is present.
What do you think the return value of this function is?

You need to return dbcon, not the value of dbGetInfo(<some argument other 
than db>).  Perhaps you meant to print the latter?: if so you need at 
explicit print() statement.


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595