[R] write.csv +RMySQL request

Fri Feb 29 16:50:34 CET 2008

The following worked for me (put together after reading ? 
textConnection). Put simply, all read/write command work with  
"connections", which are if you like "devices that know how to read  
or write things". textConnection creates such a device that writes  
(or reads if we used open="r") to/from an already existing vector.
If the file argument to write.csv is not a connection, then it is  
interpreted as a file name, and a connection to read/write on that  
file is automatically made for you. The description in ?write.csv  
explains this part.

x <- character()
y<-textConnection("x", open="w")
write.csv(iris,file=y)
close(y)

Haris Skiadas
Department of Mathematics and Computer Science
Hanover College

On Feb 29, 2008, at 4:37 AM, Tristan Casey wrote:

> Well that is certainly good news if write.csv output can be stored  
> directly to a character vector!
>
> I have tried to specify a vector within the file="" argument for  
> example;
>
> write.csv(a,file="b") where b is a preexisting character vector
>
> This does not work. Do I need to define b as something else, like a  
> textConnection?
>
>
>> Date: Fri, 29 Feb 2008 09:16:11 +0000
>> From: ripley at stats.ox.ac.uk
>> To: nub_vulcanis at hotmail.com
>> CC: jholtman at gmail.com; r-help at r-project.org
>> Subject: RE: [R] write.csv +RMySQL request
>>
>> On Fri, 29 Feb 2008, Tristan Casey wrote:
>>
>>> Ahh, my apologies I must admit that I don't fully understand
>>> textConnections fully. I have been reading up on th RODBC package  
>>> as an
>>> alternative to RMySQL.
>>>
>>> With the file argument in write.csv, are you saying it is  
>>> possible to
>>> write the csv formated data directly to a cell in a MySQL  
>>> database? I am
>>> unsure what the variable 'con' must consist of.
>>
>> No, that it is possible to write it to an R character vector.
>>
>>> Would this need to be a character string that initially connects  
>>> to the
>>> database (dbConnect) then pastes the MySQL query? I am unsure how to
>>> specify where the data is going with the file/connection argument.
>>>
>>> Thanks
>>>
>>>
>>>> Date: Fri, 29 Feb 2008 08:44:58 +0000
>>>> From: ripley at stats.ox.ac.uk
>>>> To: nub_vulcanis at hotmail.com
>>>> CC: jholtman at gmail.com; r-help at r-project.org
>>>> Subject: RE: [R] write.csv +RMySQL request
>>>>
>>>> On Fri, 29 Feb 2008, Tristan Casey wrote:
>>>>
>>>>> Thanks again for your help.
>>>>>
>>>>> I am wanting my variable to store a character string exactly as  
>>>>> the write.csv function would store as a csv text file;
>>>>>
>>>>> IE: My goal is to store a data frame of this construction;
>>>>>
>>>>> x1 x2
>>>>> 1  2
>>>>> 3 4
>>>>>
>>>>> as "X1","X2",1,2,3,4 (the same format as CSV).
>>>>>
>>>>> I am aware of the file argument, however that is the problem,  
>>>>> storing to
>>>>> a physical text file and then importing into the SQL database  
>>>>> is a very
>>>>> inefficient way of doing things, especially when I can use  
>>>>> RMySQL to
>>>>> send commands directly to the database.
>>>>
>>>> You seem however unaware of text connections.  Neither of us  
>>>> said anything
>>>> about using a 'physical text file', and the documentation for
>>>> write.csv says
>>>>
>>>>      file: either a character string naming a file or a  
>>>> connection open
>>>>            for writing.  '""' indicates output to the console.
>>>>
>>>> A 'text connection; is not a file (physical or otherwise).
>>>>
>>>>
>>>>>
>>>>> Kind Regards,
>>>>>
>>>>> Tristan Casey BPsySci (UQ)
>>>>> + 4 Festa Court, Capalaba, QLD 4157
>>>>> H 8/33 Lilly St, Greenslopes, QLD 4120
>>>>> 0450 033 948
>>>>>
>>>>>
>>>>>
>>>>>> Date: Fri, 29 Feb 2008 05:12:04 +0000
>>>>>> From: ripley at stats.ox.ac.uk
>>>>>> To: jholtman at gmail.com
>>>>>> CC: nub_vulcanis at hotmail.com; r-help at r-project.org
>>>>>> Subject: Re: [R] write.csv +RMySQL request
>>>>>>
>>>>>> On Thu, 28 Feb 2008, jim holtman wrote:
>>>>>>
>>>>>>> ?capture.output
>>>>>>>
>>>>>>> myoutput <- capture.output(write.csv(...))
>>>>>>
>>>>>> It would be better to write directly to a text connection: see  
>>>>>> the 'file'
>>>>>> argument to write.csv.
>>>>>>
>>>>>>> On Thu, Feb 28, 2008 at 7:34 PM, Tristan Casey  
>>>>>>> <nub_vulcanis at hotmail.com> wrote:
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> I am relatively new to R and learning its ins and outs. As  
>>>>>>>> part of a website I am building, I need to read and write  
>>>>>>>> csv files directly from an SQL database. Basically I want to  
>>>>>>>> convert R variables (dataframes) into CSV format, store them  
>>>>>>>> as another R variable (as a properly formatted text string  
>>>>>>>> suitable for csv reading) and then send this to one row in a  
>>>>>>>> database.
>>>>>>>>
>>>>>>>> The SQL part is fine, the problem arises because I cannot  
>>>>>>>> capture the output of write.csv! It posts to the terminal  
>>>>>>>> when file="" is used, however I also want to store it. Does  
>>>>>>>> anyone have any ideas?
>>>>>>>>
>>>>>>>> Thanks in advance!
>>>>>>
>>>>>> --
>>>>>> 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
>>>>>
>>>>> _________________________________________________________________
>>>>> Your Future Starts Here. Dream it? Then be it! Find it at  
>>>>> www.seek.com.au
>>>>> http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek% 
>>>>> 2Ecom%2Eau%2F%3Ftracking%3Dsk%3Ahet%3Ask%3Anine%3A0%3Ahot% 
>>>>> 3Atext&_t=764565661&_r=OCT07_endtext_Future&_m=EXT
>>>>
>>>> --
>>>> 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
>>>
>>> _________________________________________________________________
>>> Your Future Starts Here. Dream it? Then be it! Find it at  
>>> www.seek.com.au
>>> http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek% 
>>> 2Ecom%2Eau%2F%3Ftracking%3Dsk%3Ahet%3Ask%3Anine%3A0%3Ahot% 
>>> 3Atext&_t=764565661&_r=OCT07_endtext_Future&_m=EXT
>>
>> -- 
>> 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
>