Displaying 3 results from an estimated 3 matches for "autoquotes".
2005 Jun 22
1
substitute in a named expression
I have a 'named expression' like
expr <- expression(rep(1,d))
and would like to replace the argument d with say 5 without actually evaluating the expression. So I try substitute(expr, list(d=5)) in which case R simply returns expr which when I 'evaluate' it gives
eval(expr)
Error in rep.default(1, d) : invalid number of copies in rep()
I've looked at ?substitute and
2004 Mar 18
12
substitute question
Consider the following example:
# substitute a with b in the indicated function. Seems to work.
> z <- substitute( function()a+1, list(a=quote(b)) )
> z
function() b + 1
# z is an object of class call so use eval
# to turn it into an object of class expression; however,
# when z is evaluated, the variable a returns.
> eval(z)
function()a+1
Why did a suddenly reappear again
2007 Mar 27
7
Replacement in an expression - can't use parse()
Dear all,
Suppose I have a very long expression e. Lets assume, for simplicity, that it is
e = expression(u1+u2+u3)
Now I wish to replace u2 with x and u3 with 1. I.e. the 'new'
expression, after replacement, should be:
> e
expression(u1+x+1)
My question is how to do the replacement?
I have tried using:
> e = parse(text=gsub("u2","x",e))
> e =