[R] Matrix multiplication - code problem

MarcioRibeiro mestat at pop.com.br
Thu Apr 2 17:59:05 CEST 2009


Hi again,
I understood what you guys explained...
But, there isn't a way to do a multiplication of matrix with a FOR command
or otherelse where one o my dimension is ONE...
Well, as my data file is small, I did the procedure at the excel... But,
this is not the good procedure...
Thanks,
Marcio


Uwe Ligges-3 wrote:
> 
> 
> 
> MarcioRibeiro wrote:
>> Hi listers,
>> I am having some trouble in a matrix multiplication...
>> I have already checked some posts, but I didn't find my problem...
>> I have the following code...
>> But I am not getting the right multiplication...
>> I checked the dimension and they are fine...
>> 
>> id_y <- array(1:10,dim=c(2,1,5))
>> id_yt<-aperm(id_y,c(2,1,3))
>> m_id<-array(dim=c(dim(id_y)[1],dim(id_y)[1],dim(id_y)[3]))
>> for (i in 1:dim(id_y)[3]){
>> m_id[,,i]<-id_y[,,i]%*%id_yt[,,i]
>> }
>> m_id
>> 
>> 
> 
> 
> Due to indexing, you are loosing dimensions.
> The problem is that you expect to *loose exactly one* dimension in this 
> case (hence drop = FALSE won't be of help right away). Hence it might be 
> a good idea to know what you are going to have exactly at the end (as 
> in- and output).
> 
> Uwe Ligges
> 
> ______________________________________________
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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.
> 
> 

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