# [R] Finding Infimum in R

Peter Dalgaard pdalgd at gmail.com
Mon Apr 10 19:15:44 CEST 2017

```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
>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>>>> 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
>>>> 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
> 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

```