> 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 )
have a look at (e.g.) wilcox.test.formula:
wilcox.test.formula <-
function(formula, data, subset, na.action, ...)
{
...
m <- match.call(expand.dots = FALSE)
if(is.matrix(eval(m$data, parent.frame())))
m$data <- as.data.frame(data)
m[[1]] <- as.name("model.frame")
m$... <- NULL
mf <- eval(m, parent.frame())
...
response <- attr(attr(mf, "terms"), "response")
# And now you can get the response by mf[[-response]]
myresp <- mf[[-response]]
...
}
Torsten
>
> # 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
>
>
>
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