[R] Modifying a particular column in a tab-delimited file

[David Winsemius]

On Mar 23, 2011, at 3:44 PM, Sashi Challa wrote:

> Hi Jim,
>
> That is what I ended up doing. Each of my 1000 files has ~1 million  
> rows, and 19 columns and it was taking 85 secs for every file to be  
> just read into R.
> All I needed to do was replace one column with a particular vector  
> values. So wanted to know if there was a way to do it without  
> reading all the columns.

Learn to use awk?


> Thanks for your time,
> Sashi
>
> -----Original Message-----
> From: jim holtman [mailto:jholtman at gmail.com]
> Sent: Wednesday, March 23, 2011 11:50 AM
> To: Sashi Challa
> Cc: r-help at r-project.org
> Subject: Re: [R] Modifying a particular column in a tab-delimited file
>
> Read the whole file in, modify the column and then write the file  
> back out.
>
> On Wed, Mar 23, 2011 at 12:03 PM, Sashi Challa <challa at ohsu.edu>  
> wrote:
>> Hello R users,
>>
>> Good day!!
>>
>> I was wondering if there is a way in R to read in a particular  
>> column from a tab-delimited file, edit it and write it back into  
>> the file with all other columns intact. When I say edit I mean just  
>> replacing all the values in that column.
>> I know to read a particular column from a file using colClasses  
>> option in read.delim() function.
>> Is there any such option to write out a column into an already  
>> existing file using write.table() function ??
>>
>> Thanks for your time
>>
>> -Sashi
>


David Winsemius, MD
West Hartford, CT