colSums(X^2) -- or am I missing something? -- Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA "The business of the statistician is to catalyze the scientific learning process." - George E. P. Box
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Rossi, Peter E. > Sent: Friday, January 06, 2006 1:56 PM > To: [email protected] > Subject: [R] vectorization of groups of dot products > > > I have a set of n vectors, x_1, ..., x_n, of the same length. > I would like to form the vector of dot products -- x_1'x_1, > ..., x_n'x_n > > the fastest way I can think to do this is to put the vectors into a > matrix > and do > > diag(crossprod(X)) > > however, this seems to be very wasteful since this computes n(n+1)/2-n > unnecessary > dot products. > > Is there a better way using existing functions in R? > > thanks! > > peter > > > ................................ > Peter E. Rossi > Joseph T. and Bernice S. Lewis Professor of Marketing and Statistics > Editor, Quantitative Marketing and Economics > Rm 353, Graduate School of Business, U of Chicago > 5807 S. Woodlawn Ave, Chicago IL 60637, USA > Tel: (773) 702-7513 | Fax: (773) 834-2081 > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
