[R] Problem passing a statistical model as an argument

[Charles C. Berry]

On Thu, 20 Aug 2009, Frank E Harrell Jr wrote:

> Dear Colleagues:
>
> I would like to write a front end for a modeling function, but run into 
> trouble when passing a weights argument.

You might want to look at the code at the beginning of lm for some ideas.

Something like:

w <- function(formula, ...)
{
   mc <- match.call()
   mc[[1L]] <- as.name("lm")
   eval(mc,parent.frame())
}

might get you going.

HTH,

Chuck



>
> y <- 1:5
> x <- c(1,3,2,5,4)
>
> w <- function(formula, ...) lm(formula, ...)
> lm(y ~ x, weights=c(1,1,1,2,2))
> w(y ~ x)
> w(y ~ x, weights=c(1,1,1,2,2))
>
> Error in eval(expr, envir, enclos) :
>   ..1 used in an incorrect context, no ... to look in
>
> w <- function(formula, weights, ...) lm(formula, weights=weights, ...)
> w(y ~ x, weights=c(1,1,1,2,2))
>
> Error in model.frame.default(formula = formula, weights = weights, 
> drop.unused.levels = TRUE) :
>   invalid type (closure) for variable '(weights)'
>
> Is there a general approach that solves this?  Thanks -Frank
>
>>  sessionInfo()
> R version 2.9.0 (2009-04-17)
> x86_64-pc-linux-gnu
>
> locale:
> LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C
>
> attached base packages:
> [1] splines   stats     graphics  grDevices utils     datasets  methods
> [8] base
>
> other attached packages:
> [1] survival_2.35-4
>
> -- 
> Frank E Harrell Jr   Professor and Chair           School of Medicine
>                      Department of Biostatistics   Vanderbilt University
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901