[R] [R-sig-DB] How to save a model in DB and retrieve It

[Jeff Ryan]

A very simple option, since you're only looking to efficiently store
and retrieve, is something like a key-value store.

There is a new rredis (redis) package on CRAN, as well as the
RBerkeley (Oracle Berkeley DB) package.

RBerkeley is as simple as db_put() and db_get() calls where you
specify a key and serialize/unserialize the object before and after.

Caveat to RBerkeley is that it is only functional on *nix until
someone contributes a Windows version or insight on what I need to do
to make that work (issue is that Berkeley DB can't be compiled easily
using the R version of mingw to compile).  The package code is likely
to work for windows if you can manage to get the db headers/libs
installed with the R toolchain.

HTH
Jeff

On Fri, Apr 2, 2010 at 3:37 AM, Daniele Amberti <daniele.amberti at ors.it> wrote:
> I'm wondering how to save an object (models like lm, loess, etc) in a DB to retrieve and use it afterwards, an example:
>
> wind_ms <- abs(rnorm(24*30)*4+8)
> air_kgm3 <- rnorm(24*30, 0.1)*0.1 + 1.1
> wind_dg <- rnorm(24*30) * 360/7
> ms <- c(0:25)
> kw_mm92 <- c(0,0,0,20,94,205,391,645,979,1375,1795,2000,2040)
> kw_mm92 <- c(kw_mm92, rep(2050, length(ms)-length(kw_mm92)))
> modelspline <- splinefun(ms, kw_mm92)
> kw <- abs(modelspline(wind_ms) - (wind_dg)*2 + (air_kgm3 - 1.15)*300 + rnorm(length(wind_ms))*10)
> #plot(wind_ms, kw)
> windDat <- data.frame(kw, wind_ms, air_kgm3, wind_dg)
> windDat[windDat$wind_ms < 3, 'kw'] <- 0
> model <- loess(kw ~ wind_ms + air_kgm3 + wind_dg, data = windDat, enp.target = 10*5*3) #, span = 0.1)
>
> modX <- serialize(model, connection = NULL, ascii = T)
>
> Channel <- odbcConnect("someSysDSN; UID=aUid; PWD=aPwd")
> sqlQuery(Channel,
> paste(
> "INSERT INTO GRT.GeneratorsModels
>           ([cGeneratorID]
>           ,[tModel]
>   VALUES
>           (1,",
>           paste("'", gsub("'", "''", rawToChar(modX)), "'", sep = ''),
>           ")", sep = "") )
> # Up to this it is working correctly,
> # in DB I have the "modX" variable
> # Problem arise retrieving data and 64kb limit:
>  strQ <- "
>    SELECT  CONVERT(varchar(max), tModel) AS tModel
>    FROM    GRT.GeneratorsModels
>    WHERE   (cGeneratorID = 1)
>    "
> x <- sqlQuery(Channel, strQ, stringsAsFactors = F, believeNRows = FALSE)
> x <- sqlQuery(Channel, strQ, stringsAsFactors = F, believeNRows = FALSE) #read error
>
>
>
> Above code is working for simplier models that have a shorter representation in variable "modX".
> Any advice on how to store and retieve this kind of objects?
> Thanks
> Daniele
>
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-- 
Jeffrey Ryan
jeffrey.ryan at insightalgo.com

ia: insight algorithmics
www.insightalgo.com