This is *not* matrix multiplication, which uses %*% in R. Might that help explain your confusion?
The difference is explained in `An Introduction to R'. On Mon, 4 Oct 2004, Wayne Jones wrote: > > Hi there fellow R-users, > > Im seeing some strange behaviour when I multiply a vector by a matrix > > Here is my script: > > > tr > 1 2 3 4 5 6 > 0.2217903 0.1560525 0.1487908 0.1671354 0.1590643 0.1471667 > > > > ex1 > a b c d e f > 1 0.2309579 -3.279045 -0.6694697 -1.1024404 0.2303928 -1.5527404 > 2 -0.2865357 -2.519789 -0.1138712 -0.3571832 -2.6727913 -0.3296945 > > > is.vector(tr) > [1] TRUE > > > is.data.frame(ex1) > [1] TRUE > > > tr* ex1[1,] > a b c d e f > 1 0.05122423 -0.5117031 -0.09961092 -0.1842569 0.03664727 -0.2285117 > > > (tr* ex1)[1,] > a b c d e f > 1 0.05122423 -0.4878917 -0.1064887 -0.2445106 0.03428033 -0.2469855 > > > Notice that the output from tr * ex[1,] is different from (tr* ex1)[1,] > Especially element number 4. > > I would naturally expect both vectors to be equivalent. Why? The second multiplies the elements of ex by tr, in column-major order, and what is `natural' about that? -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [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
