[R] evaluating expressions with sub expressions

[Jennifer Young]

Hallo

I'm having trouble figuring out how to evaluate an expression when one of
the variables in the expression is defined separately as a sub expression.
Here's a simplified example

mat <- expression(0, f1*s1*g1)  # vector of formulae
g1 <- expression(1/Tm)          # expansion of the definition of g1
vals <- data.frame(f1=1, s1=.5, Tm=2) # one set of possible values for
variables

before adding this sub expression I was using the following to evaluate "mat"

sapply(mat, eval, vals)

Obviously I could manually substitute in 1/Tm for each g1 in the
definition of "mat", but the actual expression vector is much longer, and
the sub expression more complicated. Also, the subexpression is often
adjusted for different scenarios.  Is there a simple way of changing this
or redefining "mat" so that I can define "g1" like a macro to be used in
the expression vector.

Thanks!
Jennifer