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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