[R] Cause of error assigning NULL to element of a vector

[Jeff Newmiller]

Perhaps it is worth pointing out (in case the OP thinks this is SQL) that the special value NA is used for "missing" in R.

y[1] <- NA

works just fine. 
-- 
Sent from my phone. Please excuse my brevity.

On May 24, 2017 11:51:41 AM PDT, Marc Schwartz <marc_schwartz at me.com> wrote:
>
>> On May 24, 2017, at 1:30 PM, Ramnik Bansal <ramnik.bansal at gmail.com>
>wrote:
>> 
>> What is the cause of the error below ?
>> 
>>> y <- 1
>>> y[1] <- NULL
>> Error in y[1] <- NULL : replacement has length zero
>> 
>> Thanks,
>> Ramnik
>
>Hi,
>
>> length(NULL)
>[1] 0
>
>You are attempting to assign NULL, which is a zero length special
>object of its own kind, to a specific element in the vector object 'y'
>and that cannot be done.
>
>You can assign NULL to 'y':
>
>y <- NULL
>
>> y
>NULL
>
>> length(y)
>[1] 0
>
>
>BUT, 'y' is not a vector in that case:
>
>> is.vector(y)
>[1] FALSE
>
>
>
>Nor can a vector contain multiple NULLs:
>
>y <- c(NULL, NULL, NULL)
>
>> y
>NULL
>
>> length(y)
>[1] 0
>
>
>
>Similarly:
>
>y <- c(1, NULL, 1)
>
>> y
>[1] 1 1
>
>> length(y)
>[1] 2
>
>
>Perhaps reviewing ?NULL as well as:
>
>https://cran.r-project.org/doc/manuals/r-release/R-lang.html#NULL-object
>
>might also provide some insights.
>
>Regards,
>
>Marc Schwartz
>
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