On 29 December 2012 20:35, arun <smartpink...@yahoo.com> wrote: >> Is it possible to obtain the same result as X without converting X to R?
What do you mean by the same result? There is a relationship between X and R. If you express this relationship algebraically, you can get X directly using Y and Z tensors, vice versa. Too many terms in the example you have given. So I would demonstrate the possibility with a smaller example. Think of X as intermediate results from Matrix multiplication. You need to use Riemann notation instead of Einstein's [*]. However you may end up computing more terms then you need. It makes sense to use tensorA only if you know algebraic relationships well. If you think in terms of components and positioning intermediate results as most R programmers do i,e. using cbind, moving that column here in there etc,, probably tensorA is not suited for you. Hope it answers your question. [*] library(tensorA) # intermediate results via component wise multiplication set.seed(42) A <-matrix(rnorm(10), 5, 2) set.seed(43) x <-matrix(rnorm(2), 2, 1) b <- A %*% x bInter <- do.call(cbind,lapply(seq_len(dim(A)[1]),function(i) A[i,]*x)) # intermediate results via tensor multiplication set.seed(42) At <-to.tensor(rnorm(10), c(a=5, b=2)) set.seed(43) xt <-to.tensor(rnorm(2), c(c=2)) bt <- At%r%xt # Riemann sum bInterT <- t(cbind(bt[,,1][,1],bt[,,2][,2])) # Multiplication from intermediate results binterM <- t(do.call(cbind, lapply(1:5, function(i) sum(bInter[,i])))) binterTM <- t(do.call(cbind, lapply(1:5, function(i) sum(bInterT[,i])))) # Correctness # Correctness bInterT # [,1] [,2] [,3] [,4] [,5] #[1,] -0.05142981 0.02118395 -0.01362231 -0.02374106 -0.01516563 #[2,] 0.16710413 -2.38004921 0.14905054 -3.17821889 0.09874990 bInter # [,1] [,2] [,3] [,4] [,5] #[1,] -0.05142981 0.02118395 -0.01362231 -0.02374106 -0.01516563 #[2,] 0.16710413 -2.38004921 0.14905054 -3.17821889 0.09874990 b # [,1] #[1,] 0.11567432 #[2,] -2.35886526 #[3,] 0.13542823 #[4,] -3.20195995 #[5,] 0.08358427 binterM # [,1] #[1,] 0.11567432 #[2,] -2.35886526 #[3,] 0.13542823 #[4,] -3.20195995 #[5,] 0.08358427 binterTM # [,1] #[1,] 0.11567432 #[2,] -2.35886526 #[3,] 0.13542823 #[4,] -3.20195995 #[5,] 0.08358427 ______________________________________________ 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.
