Dear list,
I try to use the eval function and to understand its functionning. I tried:
xy <- "global"
f1 <- function(){
xy <- "f1"
a1 <- eval.parent(xy)
b1 <- eval(xy, sys.frame(0))
print(paste("a1 =",a1))
print(paste("b2 =",b1))
f3 <- function(){
print("----F3----")
a3 <- eval.parent(xy)
b3 <- eval(xy, sys.frame(0))
print(paste("a3 =",a3))
print(paste("b3 =",b3))
}
f2()
f3()
}
f2 <- function(){
print("----F2----")
a2 <- eval.parent(xy)
b2 <- eval(xy, sys.frame(0))
print(paste("a2 =",a2))
print(paste("b2 =",b2))
}
f1()
f2()
I obtain the following results (and add as comments what I would expect
after reading the doc). I really do not understand why the evaluation in
sys.frame(0) (i.e. global environment) did not work. Moreover, the
evaluation through eval.parent should be linked to the environment of
the caller and not the definition (so I do not understand why f2 and f3
produces different results).
> f1()
[1] "a1 = f1" ## global ?
[1] "b2 = f1" ## global
[1] "----F2----"
[1] "a2 = global" ## f1
[1] "b2 = global" ## global
[1] "----F3----"
[1] "a3 = f1" ## f1
[1] "b3 = f1" ## global
> f2()
[1] "----F2----"
[1] "a2 = global"
[1] "b2 = global"
Any help would be appreciated, Thanks.
> sessionInfo()
R version 2.15.1 (2012-06-22)
Platform: x86_64-unknown-linux-gnu (64-bit)
locale:
[1] LC_CTYPE=fr_FR.UTF-8 LC_NUMERIC=C
[3] LC_TIME=fr_FR.UTF-8 LC_COLLATE=fr_FR.UTF-8
[5] LC_MONETARY=fr_FR.UTF-8 LC_MESSAGES=C
[7] LC_PAPER=C LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=fr_FR.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] ade4_1.5-0
loaded via a namespace (and not attached):
[1] tools_2.15.1
--
Stéphane DRAY (stephane.d...@univ-lyon1.fr)
Laboratoire BBE-CNRS-UMR-5558, Univ. C. Bernard - Lyon I
43, Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
Tel: 33 4 72 43 27 57 Fax: 33 4 72 43 13 88
http://pbil.univ-lyon1.fr/members/dray/
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