[R] Finding Infimum in R

[Peter Dalgaard]

Er, 1/3, of course? (assuming that F is f). The infimum of a set is not necessarily a member of the set.

-pd

> On 10 Apr 2017, at 16:56 , Boris Steipe <boris.steipe at utoronto.ca> wrote:
> 
> Well - the _procedure_ will give a result.
> 
> But think of f(x) = {-1; x <= 1/3 and 1; x > 1/3 
> 
> What should inf{x| F(x) >= 0} be?
> What should the procedure return?
> 
> 
> 
> 
> 
>> On Apr 10, 2017, at 10:38 AM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>> 
>> Given what she said, how does the procedure I suggested fail?
>> 
>> (Always happy to be corrected).
>> 
>> -- Bert
>> Bert Gunter
>> 
>> "The trouble with having an open mind is that people keep coming along
>> and sticking things into it."
>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>> 
>> 
>> On Mon, Apr 10, 2017 at 1:57 AM, Boris Steipe <boris.steipe at utoronto.ca> wrote:
>>> Are you sure this is trivial? I have the impression the combination of an ill-posed problem and digital representation of numbers might just create the illusion that is so.
>>> 
>>> B.
>>> 
>>> 
>>> 
>>> 
>>>> On Apr 10, 2017, at 12:34 AM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>>>> 
>>>> Then it's trivial. Check values at the discontinuities and find the
>>>> first where it's <0 at the left discontinuity and >0 at the right, if
>>>> such exists. Then just use zero finding on that interval (or fit a
>>>> line if everything's linear). If none exists, then just find the first
>>>> discontinuity where it's > 0.
>>>> 
>>>> Cheers,
>>>> Bert
>>>> 
>>>> 
>>>> Bert Gunter
>>>> 
>>>> "The trouble with having an open mind is that people keep coming along
>>>> and sticking things into it."
>>>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>>> 
>>>> 
>>>> On Sun, Apr 9, 2017 at 5:38 PM, li li <hannah.hlx at gmail.com> wrote:
>>>>> Hi Burt,
>>>>>  Yes, the function is monotone increasing and points of discontinuity are
>>>>> all known.
>>>>> They are all numbers between 0 and 1.  Thanks very much!
>>>>> Hanna
>>>>> 
>>>>> 
>>>>> 2017-04-09 16:55 GMT-04:00 Bert Gunter <bgunter.4567 at gmail.com>:
>>>>>> 
>>>>>> Details matter!
>>>>>> 
>>>>>> 1. Are the points of discontinuity known? This is critical.
>>>>>> 
>>>>>> 2. Can we assume monotonic increasing, as is shown?
>>>>>> 
>>>>>> 
>>>>>> -- Bert
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> Bert Gunter
>>>>>> 
>>>>>> "The trouble with having an open mind is that people keep coming along
>>>>>> and sticking things into it."
>>>>>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>>>>> 
>>>>>> 
>>>>>> On Sun, Apr 9, 2017 at 1:28 PM, li li <hannah.hlx at gmail.com> wrote:
>>>>>>> Dear all,
>>>>>>> For a piecewise function F similar to the attached graph, I would like
>>>>>>> to
>>>>>>> find
>>>>>>>                                      inf{x| F(x) >=0}.
>>>>>>> 
>>>>>>> 
>>>>>>> I tried to uniroot. It does not seem to work. Any suggestions?
>>>>>>> Thank you very much!!
>>>>>>>  Hanna
>>>>>>> 
>>>>>>> ______________________________________________
>>>>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>>>>>>> PLEASE do read the posting guide
>>>>>>> http://www.R-project.org/posting-guide.html
>>>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>> 
>>>>> 
>>>> 
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>> 
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

-- 
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