R help - Jan 2011 - Passing in arguments into function

Hi,

I had a function that looked like:

diff <- lm(x ~ y + z)

How can I pass the argument to the 'lm' function on the fly? E.g., if I
pass it
in as a string (e.g. "x ~ y + z"), then the lm function treats it as a
string
and not a proper argument.

many thanks



      
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Hi Paul,

You need to pass the formula object, not a string.  If you have a
function that is passing one of its arguments down to lm(), just pass
the argument directly, no need to do anything special.  Here are some
examples using a built in dataset:

## wrapper function
foo <- function(fooform, ...) {
  summary(lm(formula = fooform, ...))
}

## seeing it in action
foo(mpg ~ hp * wt, data = mtcars)

## save a formula in an object
myform <- mpg ~ hp * wt

## pass the object to foo() which passes it down
foo(myform, data = mtcars)

## pass the formula object "myform" directly to lm()
summary(lm(myform, data = mtcars))

Do one of those answer your question or do what you want?

Hope this helps,

Josh

On Sun, Jan 23, 2011 at 8:46 AM, Paul Evans <p.evans48 at yahoo.com>
wrote:
> Hi,
>
> I had a function that looked like:
>
> diff <- lm(x ~ y + z)
>
> How can I pass the argument to the 'lm' function on the fly? E.g.,
if I pass it
> in as a string (e.g. "x ~ y + z"), then the lm function treats it
as a string
> and not a proper argument.
>
> many thanks
>
>
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

Isn't necessary a formula, but a class that could be coerced to that class:

x <- rnorm(100)
y <- rnorm(100)
z <- rnorm(100)
lm("x ~ y + z")


On Sun, Jan 23, 2011 at 2:46 PM, Paul Evans <p.evans48@yahoo.com> wrote:
> Hi,
>
> I had a function that looked like:
>
> diff <- lm(x ~ y + z)
>
> How can I pass the argument to the 'lm' function on the fly? E.g.,
if I
> pass it
> in as a string (e.g. "x ~ y + z"), then the lm function treats it
as a
> string
> and not a proper argument.
>
> many thanks
>
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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