R devel - Nov 2008 - what does negative indexing in a matrix mean?

Hi,

Does anyone know what the negative indexing of a matrix mean?

 

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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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
>
>
>
>
>
>
>
> This e-mail is from CIC bioGUNE. The e-mail and any files  
> transmitted with it are confidential and intended solely for the use  
> of the individual or entity to whom they are addressed. Any  
> unauthorised dissemination or copying of this e-mail or its  
> attachments, and any use or disclosure of any information contained  
> in them, is strictly prohibited and may be illegal. If you have  
> received this e-mail in error, please notify or telephone + 34 944  
> 06 13 00 and delete it from your system.
>
>
>
> 	[[alternative HTML version deleted]]
>
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