[R] multiplication question

[Peter Alspach]

Murali

I don't know about 'clever', but does this do what you want?

v1 <- 1:3
v2 <- 4:6
sum(matrix(rep(v1, length(v1)), nrow=length(v1))%*%v2)-sum(v1*v2)

Peter Alspach
 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Murali Menon
> Sent: Thursday, 3 July 2008 4:31 a.m.
> To: r-help at stat.math.ethz.ch
> Subject: [R] multiplication question
> 
> 
> folks,
>  
> is there a clever way to compute the sum of the product of 
> two vectors such that the common indices are not multiplied together?
>  
> i.e. if i have vectors X, Y, how can i compute 
>  
> Sum  (X[i] * Y[j])
> i != j
>  
> where i != j
>  
> also, what if i wanted 
>  
> Sum (X[i] * Y[j] * R[i, j])
> i != j
>  
> where R is a matrix?
>  
> thanks,
>  
> murali
>  
>  
> _________________________________________________________________
> Enter the Zune-A-Day Giveaway for your chance to win - day 
> after day after day
> 
> M_Mobile_Zune_V1
> 	[[alternative HTML version deleted]]
> 
> 

The contents of this e-mail are privileged and/or confidential to the named
 recipient and are not to be used by any other person and/or organisation.
 If you have received this e-mail in error, please notify the sender and delete
 all material pertaining to this e-mail.