Re: st: upper limit on fweights? overflowing into missing values?

[Nick Cox <njcoxstata@gmail.com>]

This is interesting, but in principle I don't see that Stata's limit
on # of observations has any bearing on how big frequency weights can
be. I can imagine people wanting to use frequency weights to subvert
the limit on number of observations.

A different point is that if there is a limit on how big weights can
be it should be documented e.g. at -help limits-.
Nick
njcoxstata@gmail.com


On 29 July 2013 00:46, Richard Williams <richardwilliams.ndu@gmail.com> wrote:
> According to -help limits-, the maximum number of observations is 2,147,483,647. Your weights give you more than 4 billion cases, well above that. Further, the help also says that this is a theoretical maximum; memory availability will certainly impose a smaller maximum.
>
> On my computer, I specified [fw = 1073741823] on the pwcorr command and it ran. Then I specified [fw = 1073741824] and it did not run. These numbers put you just below and just above the maximum number of cases that Stata allows.
>
> So in short, it appears that your fweighted cases can't exceed the 2 billion+ that Stata allows, and memory restrictions may hold you to even less than that.
>
> Also, you probably need to specify that the fweight variable is type long, e.g.
>
> input y x long fw
>
> Sent from my iPad
>
> On Jul 27, 2013, at 12:36 PM, László Sándor <sandorl@gmail.com> wrote:
>
>> Hi,
>> If you care, here is an example that silently produces missing values.
>> I notified Stata Support.
>>
>> input y x fw
>> 2 1 2147483621
>> 1 2 2147483621
>> end
>> de
>> pwcorr y x [fw=fw]
>> exit
>>
>> Thanks,
>>
>> Laszlo
>>
>> On Sun, Jul 21, 2013 at 5:08 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>>> I'd suggest documenting your problems with a reproducible example and
>>> sending Stata tech support.
>>>
>>>
>>> Nick
>>> njcoxstata@gmail.com
>>>
>>>
>>> On 21 July 2013 21:55, László Sándor <sandorl@gmail.com> wrote:
>>>> Hi,
>>>> in Stata/MP 12.1 I am getting missing values with using -pwcorr- with
>>>> -fweights- though the feature works fine with other data or if I scale
>>>> my weights down. Is it possible to simply have too large fweights,
>>>> e.g. if they cannot be of type -long- anymore?
>>>>
>>>> If so, why doesn't Stata warn me about this?
>>>>
>>>> I vaguely remember some Statalist of Stata blog discussion of this,
>>>> but I could not even Google it up, and Stata still did not warn me…
>>>>
>>>> Actually, why didn't Stata complain that I did not have integer
>>>> fweights if obviously the variable wasn't of type byte, int or long?
>>>>
>>>> Thanks,
>>>>
>>>> Laszlo
>>>>
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