On Sun, 13 Jul 2008, Juliet Hannah wrote:
I was not able to follow the solution posted. Could you demonstrate
this technique on an example
data set. Thanks!
dat <- data.frame(a = letters[1:3], b = LETTERS[1:3], c = 1:3, d = 3:1)
Using your example:
dat <- data.frame(a = letters[1:3], b = LETTERS[1:3], c = 1:3, d = 3:1)
write.csv(dat,file="yourFrame.csv")
col.pos <- match(c("b","d"),
scan("yourFrame.csv",sep=',',what=character(0),nlines=1))
Read 5 items
con <- pipe( paste( "cut -d, -f",paste(col.pos,collapse=','), "
yourFrame.csv",sep=''))
cols.b.d <- read.csv( con )
cols.b.d
b d
1 A 3
2 B 2
3 C 1
HTH,
Chuck
On Wed, Jul 2, 2008 at 1:13 PM, Charles C. Berry <[EMAIL PROTECTED]> wrote:
On Wed, 2 Jul 2008, Ben Tupper wrote:
On Jul 2, 2008, at 6:53 AM, Philip James Smith wrote:
Hi R people:
I have huge files with as many as 5000 columns. I'd really like to read
only certain columns of those files. I know column names I want to read.
I looked at the documentation of read.csv . Although there is a col.names
option, it allows users to specify the names of the columns, rather than to
pick the columns of interest.
Any suggestions on how to pick the columns I want to read only, rather
than the entire file, would be greatly appreciated.
There is a unix utility called 'cut' that enables stuff like
columns.1.3.5.to.7 <- read.csv( pipe( "cut -d, -f1,3,5-7 your.file" ) )
and using
col.pos <- match(names.of.variables.you.want,
scan("your.file", what=character(0), nlines=1 )
will enable you to set up the call to pipe.
HTH,
Chuck
Hello,
I think you want explicitly set the colClasses argument such that the
columns you *don't* want are set to NULL and all others are set to
appropriate classes.
Cheers,
Ben
Phil Smith
Duluth, GA
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive
Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
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