R devel - Aug 2019 - Potential bug in update.formula when updating offsets

Hi all,

update.formula does not seem to correctly update (i.e. remove in my case)
offset terms.

Here is an example:

update(~x + offset(z), ~ . - offset(z))
> ~x + offset(z)
Also:
update(~x, ~ . - offset(z))
> ~x + offset(z)
In both cases, I would expect the result
> ~x
as  - <term>  should remove <term> from the formula as happens for
instance
in:

update(~x + z, ~ . - z)
> ~x
I don't know if this behavior is intentional but I would say it is at least
unfortunate.

Paul

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Terry, Martin

Would this happen to be related to the "indexing term objects" issue
that has been bothering you?

-pd
> On 5 Aug 2019, at 21:44 , Paul Buerkner <paul.buerkner at gmail.com>
wrote:
> 
> Hi all,
> 
> update.formula does not seem to correctly update (i.e. remove in my case)
> offset terms.
> 
> Here is an example:
> 
> update(~x + offset(z), ~ . - offset(z))
>> ~x + offset(z)
> 
> Also:
> update(~x, ~ . - offset(z))
>> ~x + offset(z)
> 
> In both cases, I would expect the result
>> ~x
> 
> as  - <term>  should remove <term> from the formula as happens
for instance
> in:
> 
> update(~x + z, ~ . - z)
>> ~x
> 
> I don't know if this behavior is intentional but I would say it is at
least
> unfortunate.
> 
> Paul
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

Yes, it is almost certainly the same issue.? At useR I promised Martin that I
would put
together a clear example and fix for him and I have not yet done so.? I will try
to do
that this week.

 ? The heart of the issue is that in a terms object the offset expression will
apear in
the 'variables' attribute but not in the 'term.labels' or
'order' attributes, and the base
code tries to use the same subscripting vector for all 3 if then. ? The same bit
of code
shows up in update.formula and in [.formula; a fix for one can be applied to
both.

I had all this worked out, then had some problems logging into buzilla, then
sent it to
Martin about the same time 2-3 more urgent things got dumped on him, and then
we've both
let it lie. At useR he said (and I've no reason to disagree) that my prior
note was
unclear.? Let me recreate the example and fix, more carefully.

Terry T.


On 8/6/19 3:21 AM, peter dalgaard wrote:
> Terry, Martin
>
> Would this happen to be related to the "indexing term objects"
issue that has been bothering you?
>
> -pd
>
>> On 5 Aug 2019, at 21:44 , Paul Buerkner <paul.buerkner at
gmail.com> wrote:
>>
>> Hi all,
>>
>> update.formula does not seem to correctly update (i.e. remove in my
case)
>> offset terms.
>>
>> Here is an example:
>>
>> update(~x + offset(z), ~ . - offset(z))
>>> ~x + offset(z)
>> Also:
>> update(~x, ~ . - offset(z))
>>> ~x + offset(z)
>> In both cases, I would expect the result
>>> ~x
>> as  - <term>  should remove <term> from the formula as
happens for instance
>> in:
>>
>> update(~x + z, ~ . - z)
>>> ~x
>> I don't know if this behavior is intentional but I would say it is
at least
>> unfortunate.
>>
>> Paul
>>
>> 	[[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel

	[[alternative HTML version deleted]]