Grokbase Groups R r-help October 2010
FAQ
Hi All,

I have a data frame (myframe) with variables (columns) A,B,C and 100 records
(rows) for each. Column A is numeric. I would like to append a column to
myframe that subtracts the value in row 24 of A from row 1 of A. In this
procedure the first 23 rows of the new column will necessarily be blank
(NA). Can anyone provide guidance for me here?

Thanks in advance for your time.

Nick
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  • Joshua Wiley at Oct 28, 2010 at 8:31 pm
    Hi Nick,

    Take a look at ?cbind and ?"["

    Here is some (untested) code that is how I might go about it. It
    takes advantage of the fact that a single value will be recycled to
    equal the necessary length. Then I just assign over the NA in row 24.

    myframe <- cbind(myframe, New = NA)
    myframe[24, "New"] <- with(myframe, A[1] - A[24])

    New will be an all NA column except for row 24.

    Cheers,

    Josh
    On Thu, Oct 28, 2010 at 11:47 AM, Nick Ackerman wrote:

    Hi All,

    I have a data frame (myframe) with variables (columns) A,B,C and 100 records
    (rows) for each. Column A is numeric. I would like to append a column to
    myframe that subtracts the value in row 24 of A from row 1 of A. In this
    procedure the first 23 rows of the new column will necessarily be blank
    (NA). Can anyone provide guidance for me here?

    Thanks in advance for your time.

    Nick
    --
    View this message in context: http://r.789695.n4.nabble.com/How-to-perform-arithmetic-across-rows-tp3017905p3017905.html
    Sent from the R help mailing list archive at Nabble.com.

    ______________________________________________
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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/

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