All operators of the form %<something>% have the same precedence, that of %*%. R does not look at the <something> between the percent signs to determine the precedence. Hence you must use parentheses to get the order of operations that you want.
(I think that %<something>% operators are overused - providing the same functionality in a standard functional form is often more convenient. It certainly would eliminate your problem.) Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of Rainer Sachs > Sent: Monday, June 17, 2013 1:20 PM > To: r-help@r-project.org > Subject: [R] package expm: matrix powers within a product of matrices: > operation > precedence > > > package expm: matrix powers within a product of matrices: operation > precedence > > I want to double check that for M and N kxk mtrices and v a k-vector > M%^%2%*%N%*%v is not automatically read as (M%^%2)%*%N%*%v or > M%*%N%^%2%*%v is not automatically read as M%*%(N%^%2)%*%v or > both > > I had been assuming the usual precedence (powers first, then > multiplication) applies for matrix powers and multiplication in expm. I was > getting unexpected results. In desperation I tried putting in the > parentheses and seem to be getting much more reasonable answers. But I am so > surprised that the matrix power operation is, apparently, not automatically > given precedence over the matrix multiplication operation that I do not > trust that adding parentheses has cured my bug. Maybe I am still making some > other mistake instead. Can anyone confirm that in fact the parentheses are > (sometimes?) essential? I could not find any documentation, one way or the > other, just definitions of the power operator and of matrix exponentials. > > TIA Rainer K. Sachs, Prof emertitus of math > > > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/package-expm-matrix- > powers-within-a-product-of-matrices-operation-precedence-tp4669733.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.
