From pperkins@ucsd.edu  Fri Feb  9 22:04:43 2001
From: pperkins@ucsd.edu (pperkins@ucsd.edu)
Date: Fri, 9 Feb 2001 23:04:43 +0100 (MET)
Subject: [Rd] default data= arg to glm() (PR#844)
Message-ID: <200102092204.XAA08400@pubhealth.ku.dk>

Full_Name: Peter Perkins
Version: 1.2.1
OS: LinuxPPC
Submission from: (NULL) (24.4.89.36)


the lines

   if (missing(data)) 
      data <- environment(formula)

in glm() seem to contradict the documentaton:

   data: an optional data frame containing the variables in the model.
         By default the variables are taken from the environment from
         which `glm' is called.

actually, the near lack of other references to "data" is glm() is not
clear to me, so i may have this wrong.  but a small test seems to bear
out the problem:

function () 
{
	form <- y ~ x
	fun1 <- function(f)
	{
		n <- 10
		x <- runif(n, 1, 10)
		y <- rpois(n, x)
		glm(f, family=poisson(link="log"), data=environment())
	}
	fun2 <- function(f)
	{
		n <- 10
		x <- runif(n, 1, 10)
		y <- rpois(n, x)
		glm(f, family=poisson(link="log"))
	}
	print("fit1")
	print(fun1(form)$call)
	print("fit2")
	print(fun2(form)$call)
}

> test()
[1] "fit1"
glm(formula = f, family = poisson(link = "log"), data = environment())
[1] "fit2"
Error in eval(expr, envir, enclos) : Object "y" not found


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[Rd] default data= arg to glm() (PR#844)
pperkins@ucsd.edu