scoping problems (PR#614)

I am resubmitting this to r-bugs, since Thomas Lumley indicates that it
might be an error:

On Wed, 5 Jul 2000, Thomas Lumley wrote:

On Wed, 5 Jul 2000, halvorsen wrote:

Hola!

I have the following simple function:

testcar

function(pow){
           ob <- glm(Pound~CG+Age+Vage,data=car,weights=No,

subset=No>0,family=quasi(link=power(pow),var=mu^2))

           deviance(ob)
}
But trying to run it gives:

testcar(1/2)

Error in power(pow) : Object "pow" not found

'pow' isn't found because quasi() is looking for it in a strange

place.

Normally you would expect this sort of syntax to work, but the family
functions do some tricky things to allow you to specify things with or

without quotes and without or without parentheses.

I suspect this might count as a bug.

In any case, you can fix it by doing
eval(substitute(glm(Pound~CG+Age+Vage,data=car,weights=No subset=No>0,

family=quasi(link=power(pow),var=mu^2))))

As an additional note. This probably won't work if the argument to
testcar
is a variable.

A more reliable version is
 eval(substitute(glm(Pound~CG+Age+Vage,data=car,weights=No subset=No>0,
 family=quasi(link=power(pow),var=mu^2))),list(pow=pow))

( I moved the ,list argument from "substitute" to "eval" to get it
work.)

Kjetil Halvorsen

quasi

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel 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-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

  The problem is with quasi:

quasi

function (link = "identity", variance = "constant")
{
    linktemp <- substitute(link)
    if (is.expression(linktemp))
        linktemp <- eval(linktemp)
    if (!is.character(linktemp)) {
        linktemp <- deparse(linktemp)
        if (linktemp == "link")
            linktemp <- eval(link)
    }
   ...

  Note that neither of the eval's is what is wanted. At this point
  you just want to force the promise, ie evaluate the argument in
  the calling environment.
  The following piece of code seems to do that:

 > quasi

function (link = "identity", variance = "constant")
{
    linktemp <- substitute(link)
    if ( is.expression(linktemp) || is.call(linktemp) )
        linktemp <- link
    else if (!is.character(linktemp))
        linktemp <- deparse(linktemp)
    if( is.character(linktemp) )
        stats <- make.link(linktemp)
    else
        stats <- linktemp
...

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel 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-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

--
+-------------------------------------------------------------------------+
| Robert Gentleman              phone : (64-9) 3737-599 ext 3946          |
| Senior Lecturer               fax :   (64-9) 3737-018                   |
| Department of Statistics      office : Room 206 Maths/Physics           |
| University of Auckland        email : rgentlem@stat.auckland.ac.nz      |
+-------------------------------------------------------------------------+
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel 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-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._