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is there a way to read a specific column from a txt file

3 messages · Wensui Liu, Gabor Grothendieck, Paul Smith

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Sometimes, it is too costly to read the whole data file into R.
I am looking for solution in scan() and read.Lines() but don't they work.
Thank you so much!
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The sqldf package can read in a column without reading the
entire file into R.  It will automatically set up a database for you
read the file into the database (all this without going through R)
and then it will extract the column you want.
You will need two statements. One to define which
file to use and one to read in the file and extract the column.
See example 6b on the sqldf home page: http://sqldf.googlecode.com
On Sun, May 3, 2009 at 1:36 PM, Wensui Liu <liuwensui at gmail.com> wrote:
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On Sun, May 3, 2009 at 6:36 PM, Wensui Liu <liuwensui at gmail.com> wrote:
Try the following (assuming a 3 columns data file):

mydata <- read.table(file="myfile",header=T,colClasses=c(NA,"NULL",NA))

"NULL" indicates the column to be omitted.

Hope this helps you,

Paul