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: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Murali Menon > Sent: Thursday, 3 July 2008 4:31 a.m. > To: [EMAIL PROTECTED] > 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. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
