[R] getting the response (dependent) from formula?

[Jeff D. Hamann]

I'm trying to build a vector (fitting systems of equations) and I'm having a
little trouble getting the response variables from a list of formulas...

bdgmodel   <- lbdg ~ d1sqr + ld1 + lhg
hgmodel    <- lhg ~ ht2 + lht + whc
inst       <- ~ d1sqr + ld1 + ht2 + lht + whc
systemeq  <- list( bdgmodel, hgmodel )

# manually generate the y matrix...
y <- cbind( matrix( lbdg ),
            matrix( log(hg) ) )

I would like to replace the previous line with something like...

# do the three stage least squares here...
for(i in 1:length( systemeq ) )
{
    bigy <- rbind( bigy, attr(terms(systemeq[[i]]),"variables")[2] )
}

... then go on to fit the system of equations, etc, etc, etc...

attr(terms(systemeq[[i]]),"variables")[2]

this statement returns
"lbdg()" - without the quotes, which I can't figure out how to use....

is there an equivalent to model.matrix( systemeq[[1]] )?

Thanks,
Jeff.




Jeff D. Hamann
Hamann, Donald & Associates, Inc.
PO Box 1421
Corvallis, Oregon USA 97339-1421
Bus. 541-753-7333
Cell. 541-740-5988
jeff_hamann at hamanndonald.com
www.hamanndonald.com


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._