Hello I have a quick question. I need to compute matrix in R, like A <- t(X) %*% solve(V) %*% X, where X is a vector and V is a matrix This code works, but now i want to optimize it. I have try: A <- crossprod(X, solve(V)) %*% X Is there another, better way? WBR Dima [[alternative HTML version deleted]]
Since X is a vector, then A <- sum(X, solve(V, X)) is probably slightly better here. -----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Dmitrij Kudriavcev Sent: Tuesday, 29 June 2010 12:29 PM To: r-help at r-project.org Subject: [R] Matrix operations Hello I have a quick question. I need to compute matrix in R, like A <- t(X) %*% solve(V) %*% X, where X is a vector and V is a matrix This code works, but now i want to optimize it. I have try: A <- crossprod(X, solve(V)) %*% X Is there another, better way? WBR Dima [[alternative HTML version deleted]] ______________________________________________ R-help at 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.
Oops. Try A <- sum(X * solve(V, X)) (too fast!) -----Original Message----- From: Venables, Bill (CMIS, Cleveland) Sent: Tuesday, 29 June 2010 1:05 PM To: 'Dmitrij Kudriavcev'; 'r-help at r-project.org' Subject: RE: [R] Matrix operations Since X is a vector, then A <- sum(X, solve(V, X)) is probably slightly better here. -----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Dmitrij Kudriavcev Sent: Tuesday, 29 June 2010 12:29 PM To: r-help at r-project.org Subject: [R] Matrix operations Hello I have a quick question. I need to compute matrix in R, like A <- t(X) %*% solve(V) %*% X, where X is a vector and V is a matrix This code works, but now i want to optimize it. I have try: A <- crossprod(X, solve(V)) %*% X Is there another, better way? WBR Dima [[alternative HTML version deleted]] ______________________________________________ R-help at 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.