[R] Finding Infimum in R

[Boris Steipe]

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
>>>>>> 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.
>>