Yes definitely it is just matrix multiplication. However I was interested why those code going wrong.
"Attiglah, Mama" <[EMAIL PROTECTED]> wrote: I understood that you only need to multiply each row of Ret by the vector Pos but it seems that you would like to sum the resulting vector element in order to have a vector of length 500. That is merely the matrix multiplication in R!!! i.e. Ret %*% Pos. Am I getting the question wrong? Mama ----- Mama Attiglah, PhD Advanced Research Center Quantitative Research Analyst State Street Bank +44(0)20 7698 6290 (Direct Line) +44 (0)207 004 2968 (Direct Fax) Please visit our Web site at www.ssga.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Attiglah, Mama Sent: 30 January 2008 11:32 To: Megh Dal; [EMAIL PROTECTED] Subject: Re: [R] Multiplying each row of a big matrix with a vector Ret= matrix(sample( 1:1000, 500*9), nrow=500, ncol=9) Pos= c( 2593419 ,2130220, 6198197, 1673888, 1980000 , 1784732 , 2052120 ,-7490228 ,-5275000) Solution = Ret * matrix( rep(Pos, 500), nrow=500, byrow=TRUE) Use the element-wise multiplication rather than a matrix multiplication. Hope this helps. Mama ----- Mama Attiglah, PhD Advanced Research Center Quantitative Research Analyst State Street Bank +44(0)20 7698 6290 (Direct Line) +44 (0)207 004 2968 (Direct Fax) Please visit our Web site at www.ssga.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Megh Dal Sent: 30 January 2008 07:20 To: [EMAIL PROTECTED] Subject: [R] Multiplying each row of a big matrix with a vector I have a big matrix 'ret'. I want to multiply each row of it with a 2nd vector 'pos', resulting result, I want to save in a vector named 'port'. I wrote following code: > pos [1] 2593419 2130220 6198197 1673888 1980000 1784732 2052120 -7490228 -5275000 > dim(ret) [1] 500 9 > fu # user defined function function(x) { fu = x %*% t(pos) } port = apply(ret, 1, fu) > dim(port) [1] 81 500 My desire is to get port as a vector with length 500. However I am not getting that? Can anyone tell me how to correct that? Regards, --------------------------------- [[alternative HTML version deleted]] ______________________________________________ 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. ______________________________________________ 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. --------------------------------- [[alternative HTML version deleted]] ______________________________________________ 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.
