From rocket at google.com  Fri May 30 17:40:11 2008
From: rocket at google.com (rocket at google.com)
Date: Fri, 30 May 2008 17:40:11 +0200 (CEST)
Subject: [Rd] scoping problem when calling lm(precomputed formula,
	weights) from function (PR#11540)
Message-ID: <20080530154012.034B8282EFF8@mail.pubhealth.ku.dk>

I've run into a scoping problem in R.
I'm calling a function that
   * creates a formula
   * calculates a weight vector
   * calls lm with that formula and weights
This fails.

Here's a simplified reproduce example:
# f works, g doesn't, h is a workaround
rm(w)
data <- data.frame(y=runif(20), x=runif(20), z=runif(20))
f <- function(k){
  w <- data$z^k
  coef(lm(y~x, data = data, weights = w))
}
g <- function(k){
  w <- data$z^k
  Formula <- parse(text="y~x")[[1]]
  coef(lm(Formula, data = data, weights = w))
}
h <- function(k){
  w <- data$z^k
  Formula <- parse(text="y~x")[[1]]
  # Following line fails due to scoping bug.  Use workaround.
  # coef(lm(Formula, data = data, weights = w))
  Call <- paste("coef(lm(", deparse(Formula), ", data=data, weights=w))")
  eval(parse(text=Call)[[1]])
}


> f(2)
(Intercept)           x 
  0.7452512  -0.3413998 
> g(2)
Error in eval(expr, envir, enclos) : object "w" not found
> traceback()
9: eval(expr, envir, enclos)
8: eval(extras, data, env)
7: model.frame.default(formula = Formula, data = data, weights = w, 
       drop.unused.levels = TRUE)
6: model.frame(formula = Formula, data = data, weights = w, drop.unused.levels = TRUE)
5: eval(expr, envir, enclos)
4: eval(mf, parent.frame())
3: lm(Formula, data = data, weights = w)
2: coef(lm(Formula, data = data, weights = w))
1: g(2)
> h(2)
(Intercept)           x 
  0.7452512  -0.3413998 



--please do not edit the information below--

Version:
 platform = i486-pc-linux-gnu
 arch = i486
 os = linux-gnu
 system = i486, linux-gnu
 status = 
 major = 2
 minor = 7.0
 year = 2008
 month = 04
 day = 22
 svn rev = 45424
 language = R
 version.string = R version 2.7.0 (2008-04-22)

Locale:
LC_CTYPE=en_US;LC_NUMERIC=C;LC_TIME=C;LC_COLLATE=C;LC_MONETARY=C;LC_MESSAGES=en_US;LC_PAPER=en_US;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US;LC_IDENTIFICATION=C

Search Path:
 .GlobalEnv, package:stats, package:graphics, package:grDevices, package:utils, package:datasets, package:showStructure, package:Rcode, package:splus2R, package:methods, Autoloads, package:base



[Rd] scoping problem when calling lm(precomputed formula, weights) from function (PR#11540)
rocket at google.com