On 9/18/2006 1:16 PM, Evan Cooch wrote: > > Eik Vettorazzi wrote: >> test=matrix(c( expression(x^3-5*x+4), expression(log(x^2-4*x)))) >> works. > Well, not really (or I'm misunderstanding). Your code enters fine (no > errors), but I can't access individual elements - e.g., test[1,1] gives > me an error: > > > test=matrix(c( expression(x^3-5*x+4), expression(log(x^2-4*x)))) > > test[1,1] > Error: matrix subscripting not handled for this type > > Meaning...what?
Matrices in R are just vectors with a dim attribute. The matrix function let you create the matrix, but the [ function doesn't know what to do when the vector is of mode expression. This is an unimplemented case, a limitation (or perhaps bug if it wasn't intentional) in R. >> btw. you recieved an error because D expects an expression and you >> offered a list > > OK - so why then are each of the elements identified as an expression > which I print out the vector? Each element is reported to be an > expression. OK, if so, then I remain puzzled as to how this is a 'list'. The problem is that if m is a list, then m[1] is a list with one element. You wanted m[[1]] to extract the first element and get something that's not a list. Duncan Murdoch ______________________________________________ [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 and provide commented, minimal, self-contained, reproducible code.
