On Jun 21, 2011, at 12:22 AM, Joshua Wiley wrote:
On Mon, Jun 20, 2011 at 8:55 PM, Erin Hodgess
<erinm.hodg...@gmail.com> wrote:
Too funny!
how about subset?
Sure, that is one option. Each of the following will also work. The
ones wrapped with c() can easily omit more than one at a time.
mtcars[, -which(names(mtcars) == "drat")]
mtcars[, names(mtcars) != "drat"]
mtcars[, !names(mtcars) %in% c("drat")]
mtcars[, -match(c("drat"), names(mtcars))]
I like to use grep (which returns a numeric index suitable for
negating) since it generalizes better:
# exact match pattern:
mtcars[ , -grep("^drat$", names(mtcars) ) ]
#approximate, drop any name starting with "dra":
mtcars[ , -grep("^dra", names(mtcars) ) ]
#approximate, drop any name containing "dra":
mtcars[ , -grep("drat", names(mtcars) ) ]
And since the columns are actually list elements which can be
addressed as numbers these are each equivalent to:
# exact match pattern:
mtcars[ -grep("^drat$", names(mtcars) ) ]
#approximate drop any name starting with "dra":
mtcars[ -grep("^dra", names(mtcars) ) ]
#approximate, drop any name containing "dra":
mtcars[ -grep("drat", names(mtcars) ) ]
--
David
On Mon, Jun 20, 2011 at 10:52 PM, Joshua Wiley <jwiley.ps...@gmail.com
> wrote:
Hi Erin,
See inline.
On Mon, Jun 20, 2011 at 8:45 PM, Erin Hodgess <erinm.hodg...@gmail.com
> wrote:
Dear R People:
I have a data frame, xm1, which has 12 rows and 4 columns.
If I put is xm1[,-4], I get all rows, and columns 1 - 3, which is
as
it should be.
Okay, so you know how to use the column number to omit columns.
Now, is there a way to use the names of the columns to omit them,
please?
You have all the pieces (the column names, and the knowledge that
you
can omit columns by their index).
Homework: find a way to return the column numbers given the column
names (hint).
Cheers,
Josh
Thanks so much in advance!
Sincerely,
Erin
--
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodg...@gmail.com
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/
--
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodg...@gmail.com
--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
