[R] omitting columns from a data frame

[Joshua Wiley]

On Mon, Jun 20, 2011 at 8:55 PM, Erin Hodgess <erinm.hodgess at 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))]

>
> On Mon, Jun 20, 2011 at 10:52 PM, Joshua Wiley <jwiley.psych at gmail.com> wrote:
>> Hi Erin,
>>
>> See inline.
>>
>> On Mon, Jun 20, 2011 at 8:45 PM, Erin Hodgess <erinm.hodgess at 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.hodgess at gmail.com
>>>
>>> ______________________________________________
>>> R-help at 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.
>>>
>>
>>
>>
>> --
>> 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.hodgess at gmail.com
>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/