RE: [R] Writing to a file

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Tue 08 Mar 2005 - 05:22:39 EST

On Mon, 7 Mar 2005, Liaw, Andy wrote:

> Would the following do?
>
> x <- 1000
> write.table(Info[Info[,4] > x, c(1, 4)], file="/tmp/CT.dat")
>
> Andy
>
>> From: Melanie Vida
>>
>> Here is a simple question. Is there a quicker way to write to a file
>> several rows of data at a time rather than one line at a
>> time? How can
>> the code below be optimized to write several rows at a time to a file
>> rather than one line at a time. See my slow method of
>> write.table below:

There is almost no penalty in writing a line at a time *if* you open a connection and write to that. It might save you if Andy's solution runs you out of memory. I would investigate doing this is large blocks of rows in that case.

>>
>> ---------------------------
>> x<-1000
>> for( i in 1:385420)
>> (
>> if(Info[i,4] > x)
>> write.table (cbind(Info[i,1], Info[i,4], file="/tmp/CT.dat",
>> append=TRUE, row.names=FALSE, col.names=FALSE)
>>
>> Thanks,
>>
>> -Melanie
>>
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>>
>>
>
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-- 
Brian D. Ripley,                  ripley@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

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Received on Tue Mar 08 05:27:56 2005

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