On Thu, Jun 25, 2009 at 9:40 AM, reyman <reyma...@gmail.com> wrote:
> Thanks a lot for your response Peter,
>
> > I've not used these libraries, but one important question is are you
> familiar
> > with both R and python?
>
> No, i'm beginer... but i need to learn this two technology this summer,
> because this is the student job (geography/computer science student) :-]]
>
Have you considered using only R or python (and not both)? You also might
want to look at using pl/R from within postgres. Mixing database access, R,
and python in such ways can be done, but there are alternatives.
Sean
>
>
> import rpy
> rpy.set_default_mode(rpy.NO_
>>
>> CONVERSION)
>> #your code here:
>> rpy.r.library("Rdbi")
>> rpy.r.library("RdbiPgSQL")
>> rpy.r.dbConnect(rpy.r.PgSQL(),host="localhost", dbname="simpop",
>> user="postgres", password="postgres")
>> #If you want to go back to the default conversion,
>> rpy.set_default_mode(rpy.BASIC_CONVERSION)
>>
>
> Connection is ok with this code, thanks a lot to help me !
>
> Seb
>
>
> On Thu, Jun 25, 2009 at 3:20 PM, Peter <rpy-l...@maubp.freeserve.co.uk>wrote:
>
>> On Thu, Jun 25, 2009 at 2:08 PM, reyman<reyma...@gmail.com> wrote:
>> > Hello guys,
>> >
>> > I have a big project for six month, i need a little help about
>> technology
>> > imbrication ...
>> >
>> > 1) Reflexion about System architecture
>> > > a) I want to make script in python which control/launch R, R
>> access
>> > data with library "rdbi" and "RdbiPgSQL". I need this to realize simple
>> > statistics. Do you think it's better to access data in DB with R or with
>> > python in this case ?
>> > > b) I want in near futur to create an another type of script wich
>> > access data in DB with grass by R module "spgrass6" (wich interface R
>> <-->
>> > GRASS). I need this to make Spatial Analysis
>> >
>> > So with my two type of script a) and b) , you think Rpy is a good choice
>> to
>> > manipulate data/query in R and R <-> GRASS ? Have you an experience in
>> this
>> > type of plateform/architecture?
>>
>> I've not used these libraries, but one important question is are you
>> familiar
>> with both R and python?
>>
>> > 2) I have problem with RPY and connexion with my DB :
>> >
>> > from rpy import *
>> > import math
>> >
>> > r.library("Rdbi")
>> > r.library("RdbiPgSQL")
>> >
>> > r.dbConnect(r.PgSQL(),host="localhost", dbname="simpop",
>> user="postgres",
>> > password="postgres")
>> >
>> > I have this error message :
>> >
>> > Traceback (most recent call last):
>> > ...
>> > Invalid database class
>> >
>> > In R, with the same query, no error ...
>>
>> That is almost certainly due to the default object conversion, the
>> most common cause of confusion in rpy beginners.
>>
>> rPgSQL() returns some database class, which rpy has converted into a
>> simplified representation using python objects. You then try and pass
>> this back to the r.dbConnect, which means rpy has to try and turn this
>> simplified python structure back into R objects. I don't know exactly
>> what this will look like (maybe an R list), but
>> it won't be a database object!
>>
>> You should turn off the conversion.
>>
>> Try something like this:
>>
>> import rpy
>> rpy.set_default_mode(rpy.NO_CONVERSION)
>> #your code here:
>> rpy.r.library("Rdbi")
>> rpy.r.library("RdbiPgSQL")
>> rpy.r.dbConnect(rpy.r.PgSQL(),host="localhost", dbname="simpop",
>> user="postgres", password="postgres")
>> #If you want to go back to the default conversion,
>> rpy.set_default_mode(rpy.BASIC_CONVERSION)
>>
>> Peter
>>
>>
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>
>
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