I've been trying to prepare some wrappers for optimization objective functions and gradients that use try() to check for computable functions. I'm also trying to do scaling as per optim() so that a number of methods that are available on CRAN and R-Forge can use parameter and function scaling. This got me into minor trouble when I scaled a gradient or Hessian and the "inadmissible" attribute I had created suddenly disappeared. When I discovered why -- that some operations don't preserve attributes -- I started to look for a list of which ops preserve attributes and which don't. The code snippet below shows that matrix multiplication (%*%) does not, while multiplication by a vector (simple *) does. I'm not really surprised that some ops don't preserve attributes, particularly those that are binary like multiplication, but it might be nice to know which operations and special functions do so.
rm(list=ls()) m<-matrix(1:4,nrow=2, ncol=2) print(m) attributes(m) attr(m,"check")<-"***" attributes(m) bigm<-10*m str(bigm) bigm1<-diag(c(1,1))%*%m str(bigm1) bigm1<-c(1,2)*m str(bigm1) print(bigm1) arraym<-as.array(m) str(arraym) tanm<-tan(m) str(tanm) Best, John Nash ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
