I didn't get a warning. I got exactly what I sent. The NA doesn't bother me since I am interested in parsing the expression, specifically to see what is to the left of the "~" and what is to the right of the "~". I am interested in components left.name and right.name, .I am not interested in left and right. My inference from your response is that I should work with the parse tree from parse(text="y ~ a + b") rather than continue pushing latticeParseFormula.
On the other issue that you raised, I am surprised to learn that R can add factors to factors and ordered to ordered. I didn't expect either case. However, given that it can do something, I still would expect that it could add them to each other by recognizing that ordered inherits from factor. > ordered(1:3) + ordered(3:5) [1] NA NA NA > factor(1:3) + factor(3:5) [1] NA NA NA > factor(1:3) + ordered(3:5) Error in factor(1:3) + ordered(3:5) : non-numeric argument to binary operator > thank you for the prompt response. Rich ______________________________________________ [EMAIL PROTECTED] mailing list http://www.stat.math.ethz.ch/mailman/listinfo/r-devel
