[R] longer object length is not a multiple of shorter object length

Joshua Wiley jwiley.psych at gmail.com
Wed Dec 8 00:10:40 CET 2010


Hi,

On Tue, Dec 7, 2010 at 3:01 PM, madr <madrazel at interia.pl> wrote:
>
> In datamatrix[, "y"] == datamatrix[, "y"][-1] :

suppose datamatrix has 10 rows, you select column "y", and then for
the equality remove the first 'row' (technically element at this point
since you selected just column "y").  So R is being asked to try to
compare rows 1 through 10 with rows 2 through 10 hence:

>  longer object length is not a multiple of shorter object length
>
> out = c(FALSE,datamatrix[,'y'] == datamatrix[,'y'][-1])
>
> and I do not know why I get that error, the resulting out matrix is somehow
> one row larger than datamatrix...
> all I try to do is filter matrix by dropping rows where [,'y'][-1] ==
> [,'y'][+1]

perhaps you want to compare rows 1 through 9 with 2 through 10?  That
is, see if there are any differences?  Following through wtih there
being 10 rows, you could remove the last one (replacing 10 with
however many you actually have):

datamatrix[, "y"][-10] == datamatrix[, "y"][-1]

or alternately you might look at the ?diff function:

diff(datamatrix[, "y"])

which will calculate differences based on the set lag (1 by default).
It seems like you might be interested in something like that.

Cheers,

Josh

> --
> View this message in context: http://r.789695.n4.nabble.com/longer-object-length-is-not-a-multiple-of-shorter-object-length-tp3077400p3077400.html
> Sent from the R help mailing list archive at Nabble.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/



More information about the R-help mailing list