From ggrothendieck at gmail.com  Fri May 30 19:56:13 2008
From: ggrothendieck at gmail.com (Gabor Grothendieck)
Date: Fri, 30 May 2008 13:56:13 -0400
Subject: [Rd] scoping problem when calling lm(precomputed formula,
	weights) from function (PR#11540)
In-Reply-To: <20080530154012.034B8282EFF8@mail.pubhealth.ku.dk>
References: <20080530154012.034B8282EFF8@mail.pubhealth.ku.dk>
Message-ID: <971536df0805301056i38c70847m3c77acec807048e8@mail.gmail.com>

Try replacing the last line in g with:

lmout <- do.call(lm, list(Formula, data = data, weights = w))
coef(lmout)

or replace w with environment()$w thereby explicitly telling it where to look.


On Fri, May 30, 2008 at 11:40 AM,  <rocket at google.com> wrote:
> 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
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>



[Rd] scoping problem when calling lm(precomputed formula, weights) from function (PR#11540)
Gabor Grothendieck