Hello R-team ~
I ran across an inconsistency about how within( ) handles expressions
like b<-NULL. (I have found within( ) very handy, by the way.) The
problem appears to crop up when you use something like b<-NULL in the
same within() call that creates a new variable in the data frame. An
example using 2.6.2 on Windows XP is below. Version 2.6.1 had a
different, but similar problem.
As always, thanks for a very useful piece of software.
Joe Ritter
> a<-1:5;b<-2:6;c<-3:7
> abc=data.frame(a,b,c)
> within(abc,{b<-NULL})
a c
1 1 3
2 2 4
3 3 5
4 4 6
5 5 7
> within(abc,{d<-a+7;b<-NULL})
a c d structure(c(" 8", " 9", "10",
"11", "12"), class = "AsIs")
1 1 3 NULL 8
2 2 4 <NA> 9
3 3 5 <NA> 10
4 4 6 <NA> 11
5 5 7 <NA> 12
Warning message:
In format.data.frame(x, digits = digits, na.encode = FALSE) :
corrupt data frame: columns will be truncated or padded with NAs
> within(abc,{a<-a+7;b<-NULL})
a c
1 8 3
2 9 4
3 10 5
4 11 6
5 12 7