# [R] Finding a Diff within a Dataframe columns

jim holtman jholtman at gmail.com
Mon Jan 31 20:10:42 CET 2011

```I see that others have already responded, but will add my point of
view.  You indicated that you wanted to take the difference between
pairs of columns and did not specify exactly how many there were; in
your example there were 4 columns (2 pairs).  If there were only two,
then the solution from Dennis would be the way to go because it is
explicit in what has to be done.  I just created a list of the "odd"
columns [seq(from = 1, by = 2, length = ncol(x) %/%2)] trying to take
care of any odd number of columns.  This was then used in the 'sapply'
to iterate over the columns.

On Sun, Jan 30, 2011 at 10:49 PM, Ramya <ramya.victory at gmail.com> wrote:
>
> Hi jholtman,
>
> Thanks a ton it just worked. if you dont mind can you explain the code it a
> little
> sapply(seq(from = 1, by = 2, length = ncol(x) %/% 2), function(a){
> +     x[[a]] - x[[a + 1]]
> + })
>
> wat is the purpose of double percent sign and is the sapply the function we
> generally use for the Dataframe?
>
> Thanks
> Ramya
> --
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>
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--
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?

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