On 12-04-19 3:11 PM, harry mamaysky wrote:
I am new to R, and I have been running into the following situation
when I mistype a variable name in some code:
list1<- list( a=1, b=2 )
list2<- list( a=1 )
list2$b<- list1$c
list2
$a
[1] 1
I would think at the point where I am trying to reference a field
called "c" -- that does not exist -- in list1, there would be an error
flagged.
Not intending to be snarky, but you should read the documentation, which
does describe this.
Instead, list1$c returns value NULL, and the assignment "list2$b<-
NULL" does not return any error, but also does not create a field
called "b" in list2.
Is there a way to have R flag the reference to field "c" in list1 as an error?
No there isn't. You get a bit more support if you index by number:
list1[[3]] will give an error (though assigning into list2[[2]] will
make list2 bigger).
Duncan Murdoch
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