[R] multiplication question
Peter Alspach
PAlspach at hortresearch.co.nz
Wed Jul 2 22:54:04 CEST 2008
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.
More information about the R-help
mailing list