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
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