[R] Reading large files

[Gabor Grothendieck]

Note that the filter= argument on read.csv.sql can be used to pass the
input through a filter written in perl, [g]awk or other language.
For example: read.csv.sql(..., filter = "gawk -f myfilter.awk")

gawk has the FIELDWIDTHS variable for automatically parsing fixed
width fields, e.g.
http://www.delorie.com/gnu/docs/gawk/gawk_44.html
making this very easy but perl or whatever you are most used to would
be fine too.

On Fri, Feb 5, 2010 at 8:50 PM, Vadlamani, Satish {FLNA}
<SATISH.VADLAMANI at fritolay.com> wrote:
> Hi Gabor:
> Thanks. My files are all in fixed width format. They are a lot of them. It would take me some effort to convert them to CSV. I guess this cannot be avoided? I can write some Perl scripts to convert fixed width format to CSV format and then start with your suggestion. Could you let me know your thoughts on the approach?
> Satish
>
>
> -----Original Message-----
> From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com]
> Sent: Friday, February 05, 2010 5:16 PM
> To: Vadlamani, Satish {FLNA}
> Cc: r-help at r-project.org
> Subject: Re: [R] Reading large files
>
> If your problem is just how long it takes to load the file into R try
> read.csv.sql in the sqldf package.  A single read.csv.sql call can
> create an SQLite database and table layout for you, read the file into
> the database (without going through R so R can't slow this down),
> extract all or a portion into R based on the sql argument you give it
> and then remove the database.  See the examples on the home page:
> http://code.google.com/p/sqldf/#Example_13._read.csv.sql_and_read.csv2.sql
>
> On Fri, Feb 5, 2010 at 2:11 PM, Satish Vadlamani
> <SATISH.VADLAMANI at fritolay.com> wrote:
>>
>> Matthew:
>> If it is going to help, here is the explanation. I have an end state in
>> mind. It is given below under "End State" header. In order to get there, I
>> need to start somewhere right? I started with a 850 MB file and could not
>> load in what I think is reasonable time (I waited for an hour).
>>
>> There are references to 64 bit. How will that help? It is a 4GB RAM machine
>> and there is no paging activity when loading the 850 MB file.
>>
>> I have seen other threads on the same types of questions. I did not see any
>> clear cut answers or errors that I could have been making in the process. If
>> I am missing something, please let me know. Thanks.
>> Satish
>>
>>
>> End State
>>> Satish wrote: "at one time I will need to load say 15GB into R"
>>
>>
>> -----
>> Satish Vadlamani
>> --
>> View this message in context: http://n4.nabble.com/Reading-large-files-tp1469691p1470667.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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>