[Rd] what does negative indexing in a matrix mean?
Simon Urbanek
simon.urbanek at r-project.org
Wed Nov 12 17:42:36 CET 2008
On Nov 12, 2008, at 11:28 , Itziar Frades Alzueta wrote:
> Hi,
>
> Does anyone know what the negative indexing of a matrix mean?
>
>
?`[`
For '['-indexing only: 'i, j, ...' can be logical vectors,
indicating elements/slices to select. Such vectors are
recycled if necessary to match the corresponding extent. 'i,
j, ...' can also be negative integers, indicating
elements/slices to leave out of the selection.
.. so in your case you're removing one of the predictors (and I don't
think you really have a matrix there ...).
Cheers,
S
>
> I am using the RWeka and this evaluate classifier does not work on new
> data like this
>
>
>
> e <- evaluate_Weka_classifier(m1235,newdata=XW4, complexity =
> FALSE,class = FALSE)
>
>
>
> while it work with negative indexing:
>
>
>
> e <- evaluate_Weka_classifier(m1235,newdata=XW4[,-2], complexity =
> FALSE,class = FALSE)
>
>
>
> Although I do not understand what negative indexing of a matrix means,
> or whether it produces any transformation.
>
>
>
> Regards,
>
>
>
> Itziar Frades
>
>
>
>
>
>
>
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