[R] How to read only specified columns from a data file

[David Winsemius]

On Mar 15, 2011, at 1:11 PM, <rex.dwyer at syngenta.com> wrote:

> I think you need to read an introduction to R.
> For starters, read.table returns its results as a value, which you  
> are not saving.
> The probable answer to your question:
> Read the whole file with read.table, and select columns you need,  
> e.g.:
> tab <- read.table(myfile, skip=2)[,1:5]
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org 
> ] On Behalf Of Luis Ridao
> Sent: Tuesday, March 15, 2011 11:53 AM
> To: r-help at r-project.org
> Subject: [R] How to read only specified columns from a data file
>
> R-help,
>
> I'm trying to read a data file with plenty of columns.
> I just need the first 5 but it doe not work by doing something like:
>
>> mycols <- rep(NULL, 430) ; mycols[c(1:4)] <- NA
>> read.table(myfile, skip=2, colClasses=mycols)

I would have suggested:

mycols <- rep(NULL, 430) ; mycols[1:5] <- rep("numeric", 5)
inp <- read.table(myfile, skip=2, colClasses=mycols)
head(inp)

-- 
David.

>
> Any suggestions?
>
> Thanks in advance
>
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David Winsemius, MD
West Hartford, CT